Stanford Encyclopedia of Philosophy
Charles Sanders Peirce
First published Fri Jun 22, 2001; substantive revision Wed  Nov 12, 2014
 
Charles Sanders Peirce (1839–1914) was the founder of American pragmatism  
(after about 1905 called by Peirce “pragmaticism” in order to differentiate 
his  views from those of William James, John Dewey, and others, which were 
being  labelled “pragmatism”), a theorist of logic, language, 
communication, and the  general theory of signs (which was often called by 
Peirce “
semeiotic”), an  extraordinarily prolific logician (mathematical and general), 
and 
a developer of  an evolutionary, psycho-physically monistic metaphysical 
system. Practicing  geodesy and chemistry in order to earn a living, he 
nevertheless considered  scientific philosophy, and especially logic, to be his 
true calling, his real  vocation. In the course of his polymathic researches, 
he wrote voluminously on  an exceedingly wide range of topics, ranging from 
mathematics, mathematical  logic, physics, geodesy, spectroscopy, and 
astronomy, on the one hand (that of  mathematics and the physical sciences), to 
psychology, anthropology, history,  and economics, on the other (that of the 
humanities and the social  sciences).
 
    *   _1. Brief  Biography_ 
(http://plato.stanford.edu/entries/peirce/#bio)  
    *   _2. Difficulty  of Access to Peirce's Writings_ 
(http://plato.stanford.edu/entries/peirce/#access)  
    *   _3. Deduction,  Induction, and Abduction_ 
(http://plato.stanford.edu/entries/peirce/#dia)  
    *   _4. Pragmatism,  Pragmaticism, and the Scientific Method_ 
(http://plato.stanford.edu/entries/peirce/#prag)  
    *   _5.  Anti-determinism, Tychism, and Evolutionism_ 
(http://plato.stanford.edu/entries/peirce/#anti)  
    *   _6. Synechism, the  Continuum, Infinites, and Infinitesimals_ 
(http://plato.stanford.edu/entries/peirce/#syn)  
    *   _7. Probability,  Verisimilitude, and Plausibility_ 
(http://plato.stanford.edu/entries/peirce/#prob)  
    *   _8.  Psycho-physical Monism and Anti-nominalism_ 
(http://plato.stanford.edu/entries/peirce/#psych)  
    *   _9. Triadism and  the Universal Categories_ 
(http://plato.stanford.edu/entries/peirce/#triad)  
    *   _10. Mind and  Semeiotic_ 
(http://plato.stanford.edu/entries/peirce/#mind)  
    *   _11. Semeiotic and  Logic_ 
(http://plato.stanford.edu/entries/peirce/#seme)  
    *   _12. The  Classification of the Sciences_ 
(http://plato.stanford.edu/entries/peirce/#class)  
    *   _13.  Logic_ (http://plato.stanford.edu/entries/peirce/#logic)  
    *   _14. Peirce's  Reduction Thesis_ 
(http://plato.stanford.edu/entries/peirce/#red)  
    *   _15. Contemporary  Practical Application of Peirce's Ideas_ 
(http://plato.stanford.edu/entries/peirce/#con)  
    *   _16. Significant  Students of Peirce_ 
(http://plato.stanford.edu/entries/peirce/#stud)  
    *   _Bibliography_ (http://plato.stanford.edu/entries/peirce/#Bib)  
    *   _Academic  Tools_ (http://plato.stanford.edu/entries/peirce/#Aca)  
    *   _Other Internet  Resources_ 
(http://plato.stanford.edu/entries/peirce/#Oth)  
    *   _Related  Entries_ (http://plato.stanford.edu/entries/peirce/#Rel) 
 
____________________________________

 
1. Brief Biography
Charles Sanders Peirce was born on September 10, 1839 in Cambridge,  
Massachusetts, and he died on April 19, 1914 in Milford, Pennsylvania. His  
writings extend from about 1857 until near his death, a period of approximately 
 
57 years. His published works run to about 12,000 printed pages and his known 
 unpublished manuscripts run to about 80,000 handwritten pages. The topics 
on  which he wrote have an immense range, from mathematics and the physical 
sciences  at one extreme, to economics, psychology, and other social 
sciences at the other  extreme. 
Peirce's father Benjamin Peirce was Professor of Mathematics at Harvard  
University and was one of the founders of, and for a while a director of, the 
U.  S. Coast and Geodetic Survey as well as one of the founders of the 
Smithsonian  Institution. The department of mathematics at Harvard was 
essentially built by  Benjamin. From his father, Charles Sanders Peirce 
received most 
of the substance  of his early education as well as a good deal of 
intellectual encouragement and  stimulation. Benjamin's didactic technique 
mostly 
took the form of setting  interesting problems for his son and checking 
Charles's solutions to them. In  this challenging instructional atmosphere 
Charles 
acquired his lifelong habit of  thinking through philosophical and 
scientific problems entirely on his own. To  this habit, perhaps, is to be 
attributed 
Charles Peirce's considerable  originality. 
Peirce graduated from Harvard in 1859 and received the bachelor of science  
degree in chemistry in 1863, graduating summa cum laude. Except for his  
remarkable marks in chemistry Peirce was a poor student, typically in the 
bottom  third of his class. Obviously, the standard curriculum bored him, so 
that he  mostly avoided doing seriously its required work. For thirty-two 
years, from  1859 until the last day of 1891, he was employed by the U. S. 
Coast 
and Geodetic  Survey, mainly surveying and carrying out geodetic 
investigations. Some of this  work Peirce undertook simply to finance his 
diurnal 
existence (and that of his  first wife Melusina (Zina) Fay), while he devoted 
the 
main force of his thinking  to abstract logic. Nevertheless, the geodetic 
tasks involved making careful  measurements of the intensity of the earth's 
gravitational field by means of  using swinging pendulums. The pendulums that 
Peirce used were often of his own  design. For over thirty years, then, 
Peirce was involved in practical and  theoretical problems associated with 
making very accurate scientific  measurements. This practical involvement in 
physical science was crucial in his  ultimately coming to reject scientific 
determinism, as we shall see. 
>From 1879 until 1884, Peirce maintained a second job teaching logic in the  
Department of Mathematics at Johns Hopkins University. During that period 
the  Department of Mathematics was headed by the famous mathematician J. J.  
Sylvester, whom Peirce had met earlier through his father Benjamin. This  
teaching period also was characterized by Peirce's having several students who 
 made names for themselves in their own right. Among these were Oscar 
Howard  Mitchell, Allan Marquand, Benjamin Ives Gilman, Joseph Jastrow, Fabian 
Franklin,  Christine Ladd (later, after having married Fabian Franklin, 
Christine  Ladd-Franklin), Thorstein Veblen, and John Dewey. Brief commentary 
will 
be  offered at the end of this essay on three of these figures: John Dewey, 
Oscar  Howard Mitchell, and Christine Ladd. It is sometimes said that 
William James was  also one of Peirce's students, but this claim is erroneous: 
it 
conflates the  fact of James's being an old and a close friend of Peirce, 
as well as being a  fellow-member with Peirce in the so-called “Metaphysical 
Club” in Cambridge,  Massachusetts, with the non-fact of James's being a 
student of Peirce at Johns  Hopkins University along with John Dewey and 
others. 
Peirce's teaching job at Johns Hopkins was suddenly terminated for reasons  
that are apparently connected with the fact that Peirce's second wife 
(Juliette  Annette Froissy, a.k.a. Juliette Annette Pourtalai) was a Gypsy, 
moreover a  Gypsy with whom Peirce had more or less openly cohabited before 
marriage and  before his divorce from his first wife Zina. (In fact Peirce 
obtained his  divorce from Zina only two days before marrying Juliette.) The 
Johns 
Hopkins  position was Peirce's only academic employment, and after losing 
it Peirce  worked thereafter only for the U. S. Coast and Geodetic Survey 
(and constructing  entries for the Century Dictionary) and writing book reviews 
for the  Nation. The government employment came to an end the last day of 
1891,  ultimately because of funding objections to pure research (and perhaps 
also to  Peirce's extravagant spending and to his procrastination in 
finishing his  required reports) that were generated in an 
ever-practical-minded 
Congress.  Thereafter, Peirce often lived on the edge of penury, eking out a 
living doing  intellectual odd-jobs (such as translating or writing 
occasional pieces) and  carrying out consulting work (mainly in chemical 
engineering 
and analysis). For  the remainder of his life, except for money inherited 
from his mother and aunt,  Peirce was often in dire financial straits; 
sometimes he managed to survive only  because of the overt or covert charity of 
relatives or friends, for example that  of his old friend William James. 
In his youth Peirce was amazingly precocious, and he began to study logic  
seriously at an extraordinarily early age. According to noted Peirce scholar 
Max  Fisch in his“Introduction” to Volume 1 of The Writings of Charles S. 
Peirce:  A Chronological Edition, p. xviii, Peirce's introduction to and 
first  immersion in the study of logic came in 1851 within a week or two of his 
turning  12 years of age. Remembering the occasion in 1910, in his “Note on 
the Doctrine  of Chances,” in Collected Papers of Charles S. Peirce, Volume 
II,  Section 408 (hereinafter such Collected Papers references will be 
cited  as CP, 2.408), Peirce himself remembered the crucial event as having  
occurred in 1852, when he was 13 years old. Regardless of his exact age, at the 
 time of the event Charles encountered and then over a period of at most a 
few  days studied and absorbed a standard textbook of the time on logic by 
Bishop  Richard Whately. Having become fascinated by logic, he began to think 
of all  issues as problems in logic. During his freshman year at college 
(Harvard), in  1855, when he was 16 years old, he and a friend began private 
study of  philosophy in general, starting with Schiller's Letters on the 
Aesthetic  Education of Man and continuing with Kant's Critique of Pure  
Reason. 
Schiller's distinction among the three basic human drives of  Stofftrieb, 
Formtrieb, and Speiltrieb Peirce never  forgot or renounced, and it became 
the basis for Peirce's distinction between  the man of practical affairs, the 
man of scientific activity, and the man of  aesthetic practice. By Kant 
Peirce was initially more or less repelled. After  three years of intense study 
of Kant, Peirce concluded that Kant's system was  vitiated by what he called 
its “puerile logic,” and about the age of 19 he  formed the fixed 
intention of devoting his life to the study of and to research  in logic. It 
was, 
however, impossible at that time, as indeed Peirce's father  Benjamin informed 
him, to earn a living as a research logician; and Peirce  described himself 
at the time of his graduation from Harvard in 1859, just short  of his 20th 
birthday, as wondering “what I would do in life.” Within two years,  
however, he had more or less resolved his problem. During those two years he 
had  
worked as an Aid on the Coast Survey, in Maine and Louisiana, then had 
returned  to Cambridge and had studied natural history and natural philosophy 
at 
Harvard.  He said of himself that in 1861 he “No longer wondered what I 
would do in life  but defined my object.” It is evident that his adoption of 
the profession of  chemistry and his practice of geodesy allowed Charles both 
to support himself  (and before long also his first wife Zina) and to 
continue to engage in  researches on logic. From the early 1860's until his 
death 
in 1914 his output in  logic was voluminous and varied. One of his logical 
systems became the basis for  Ernst Schroeder's great three-volume treatise 
on logic, the Vorlesungen  ueber die Algebra der Logik. 
Peirce, then, had early and deep disagreements with Kant's position about  
logic, and he never altered his view that Kant's view of logic was 
superficial:  “… he [i.e. Kant] never touches this last doctrine [i.e. logic] 
without  betraying marks of hasty, superficial study” (Collected Papers of 
Charles 
 Sanders Peirce, Volume 2, Section 3; hereafter such Collected  Papers 
references will be cited as as CP, 2.3). Even worse, Peirce  held, was the 
Logik 
of Hegel: Kant's fault “… is a hundredfold more  true of Hegel's Logik … 
. That work cannot justly be regarded as  anything more than a sketch” (CP, 
2.32). 
Nevertheless, Peirce continued to respect and read the first  Critique 
throughout his life. For a fuller discussion of Peirce's own  views about how 
his work related to that of Kant, Hegel, and Schelling, see the  supplementary 
document: 
_Peirce's  View of the Relationship Between His Own Work and German 
Idealism_ 
(http://plato.stanford.edu/entries/peirce/self-contextualization.html)  
2. Difficulty of Access to Peirce's Writings
Peirce's extensive publications are scattered among various publication  
media, and have been difficult to collect. Shortly after his death in 1914, 
his  widow Juliette sold his unpublished manuscripts to the Department of 
Philosophy  at Harvard University. Initially they were under the care of Josiah 
Royce, but  after Royce's death in 1916, and especially after the end of the 
First World  War, the papers were poorly cared for. Many of them were 
misplaced, lost, given  away, scrambled, and the like. Carolyn Eisele, one of 
several genuine heroes in  the great effort to locate and assemble Peirce's 
writings, discovered a lost  trunk full of Peirce's papers and manuscripts only 
in the mid-1950s; the trunk  had been secreted, apparently for decades, in 
an unlit, obscure part of the  basement in Harvard's Widener Library. 
In the 1930's volumes of The Collected Papers of Charles Sanders  Peirce 
began to appear, with Charles Hartshorne, Paul Weiss, and Arthur  Burks as 
their editors. For almost three decades these volumes, and various  collections 
of entries culled from them were the only generally available source  for 
Peirce's thoughts. Unfortunately, many of the entries in the Collected  
Papers are not integral pieces of Peirce's own design, but rather stretches  of 
writing that were cobbled together by the editors at their own discretion  
(sometimes one might almost say “whim”) from different Peircean sources. 
Often a  single entry will consist of patches of writing from very different 
periods of  Peirce's intellectual life, and these patches might even be in 
tension or  outright contradiction with each other. Such entries in the 
Collected  Papers make very difficult reading if one tries to regard them as  
consistent, sustained passages of argument. They also tend to give the reader a 
 
false picture of Peirce as unsystematic, desultory, and unable to complete a  
train of thought. In general, even though Peirce is often obscure and even 
at  his best is seldom easy to read, the Collected Papers make Peirce's  
thinking look much more obscure than it really is. 
The only sensible and intelligent way to publish the works of someone like  
Peirce, who wrote voluminously and over such a long period of time (57 
years),  is to arrange the publication chronologically and to employ extremely 
careful  editing. In such a fashion, the entire set of Peircean works can be 
presented,  as Peirce conceived them and in their natural temporal setting 
and order.  Finally, beginning in 1976 with the organizational conception of 
Max H. Fisch  and the help of Edward Moore, the Peirce Dition Project (PEP) 
was created at  Indiana University-Purdue University at Indianapolis 
(UIPUI). Then, under the  PEP, in the 1980s, there began to appear a 
meticulously 
edited chronological  edition of carefully selected works of Peirce: this is 
the Writings of  Charles S. Peirce: a Chronological Edition, edited by The 
Peirce Edition  Project of the Indiana University-Purdue University at 
Indianapolis. Although  the Chronological Edition has been fettered from time 
to 
time by lack  of proper funding, the Chronological Edition has succeeded in 
covering  extremely well in its first seven published volumes the major 
writings from 1857  to 1892. (At the present time, October 2014, Volume 7 is 
still awaiting  publication, even though Volume 8, covering writings from 1890 
to 1892 already  has been published. Volume 7 is to be an edition of Peirce's 
definitions for the  Century Dictionary. It is to be edited by the Peirce 
Edition Project in  conjunction with the University of Quebec at Montreal 
(UQAM)), under the  supervision of Professor Francois Latraverse.) The 
impressive achievement of the  PEP is finally making it possible to assess the 
real 
Peirce, instead of the  chopped-up and then re-pasted-together picture of 
previously available of  Peirce. In particular the Chronological Edition has 
made it possible to  see the development of Peirce's thinking from its 
earliest stages to its later  developments. Questions long vexed in Peirce 
scholarship are finally beginning  to be debated usefully by Peirce scholars: 
whether there is genuine systematic  unity in Peirce's thought, whether his 
ideas 
changed or remained the same over  time, in what particulars his thought 
did change and why, when exactly certain  notions were first conceived by 
Peirce, whether there were definite “periods” in  Peirce's intellectual 
development, and what exactly Peirce meant by some of his  more obscure notions 
such as his universal categories (on which see below).  Continued funding for 
the Peirce Edition Project is obviously a crucial priority  in the ongoing 
effort to bring to public light the thoughts of this extremely  important 
American philosopher. 
In addition to the Chronological Edition of the Peirce Edition  Project, 
other venues for editing and publishing Peirce's work are regularly  found, 
and there are several excellent editions of particular lectures,  
lecture-series, chains of correspondence, and the like. Just four such editions 
 will be 
mentioned here. First, there is the edition of Peirce's Cambridge  
Conferences Lectures of 1898, edited by Kenneth Laine Ketner and with a forward 
 by 
Hilary Putnam, entitled Reasoning and the Logic of Things. Second,  there is 
the edition of Peirce's Harvard Lectures on Pragmatism of 1903, edited  by 
Patricia Ann Turrisi, entitled Pragmatism as a Principle and Method of  
Right Thinking. Third, there is the four-volume edition of Peirce's  
mathematical writings edited by Carolyn Eisele, entitled The New Elements of  
Mathematics by Charles S. Peirce. Fourth, there is the two-part edition of  
Peirce's 
writings on the history and logic of science edited by Carolyn Eisele,  
entitled Historical Perspectives on Peirce's Logic of Science: A History of  
Science. 
3. Deduction, Induction, and Abduction
Prior to about 1865, thinkers on logic commonly had divided arguments into  
two subclasses: the class of deductive arguments (a.k.a. necessary 
inferences)  and the class of inductive arguments (a.k.a. probable inferences). 
About this  time, Peirce began to hold that there were two utterly distinct 
classes of  probable inferences, which he referred to as inductive inferences 
and abductive  inferences (which he also called hypotheses and retroductive 
inferences). Peirce  reached this conclusion by entertaining what would happen 
if one were to  interchange propositions in the syllogism AAA-1 (Barbara): 
All Ms are  Ps; all Ss are Ms; therefore, all Ss are  Ps. This valid 
syllogism Peirce accepted as representative of  deduction. But he also seemed 
typically to regard it in connection with a  problem of drawing conclusions on 
the basis of taking samples. For let us regard  being an M as being a member 
of a population of some sort, say being a  ball of the population of balls in 
some particular urn. Let us regard P  as being some property a member of 
this population can have, say being red. And,  finally, let us regard being an 
S as being a member of a random sample  taken from this population. Then 
our syllogism in Barbara becomes: All balls in  this urn are red; all balls in 
this particular random sample are taken from this  urn; therefore, all 
balls in this particular random sample are red. Peirce  regarded the major 
premise here as being the Rule, the minor premise as being  the particular 
Case, 
and the conclusion as being the Result of the argument. The  argument is a 
piece of deduction. In this example the argument is also an  argument from 
population to random sample that is also a necessary  inference. 
But now let us see what happens if we form a new argument by interchanging  
the conclusion (the Result) with the major premise (the Rule). The 
resultant  argument becomes: All Ss are Ps (Result); all Ss are  Ms (Case); 
therefore, all Ms are Ps (Rule). This is  the invalid syllogism AAA-3. But let 
us 
now construe it as pertaining to drawing  conclusions on the basis of taking 
samples. The argument then becomes: All balls  in this particular random 
sample are red; all balls in this particular random  sample are taken from this 
urn; therefore, all balls in this urn are red. What  we have here is an 
argument from sample to population. This sort of argument is  what Peirce 
understood to be the core meaning of induction. That is to say, for  Peirce, 
induction in the most basic sense is argument from random sample to  
population. 
It should be clear that inductive inference is not necessary  inference: it 
might well turn out that the claims stated in the premises are  true even 
though the claim made in the conclusion is false. 
Let us now go further and see what happens if, from the deduction AAA-1, we 
 form a new argument by interchanging the conclusion (the Result) with the 
minor  premise (the Case). The resultant argument becomes: All Ms are  Ps 
(Rule); all Ss are Ps (Result); therefore, all  Ss are Ms (Case). This is the 
invalid syllogism AAA-2. But let  us now regard it as pertaining to drawing 
conclusions on the basis of taking  samples. The argument then becomes: All 
balls in this urn are red; all balls in  this particular random sample are 
red; therefore, all balls in this particular  random sample are taken from 
this urn. What we have here is nothing at all like  an argument from 
population to sample or an argument from sample to population:  rather, it is a 
form 
of probable argument entirely different from both deduction  and induction. 
It has the air of conjecture or “educated guess” about it. This  new type 
of argument Peirce called hypothesis (also, retroduction, and also,  
abduction). It should be clear that abduction is never necessary inference 
There is no need to consider the variant of AAA-1 that is obtained by  
interchanging the Rule and the Case in AAA-1. The resultant argument is of the  
form AAA-4, which is exactly the same argument as AAA-1 with interchanged  
premises. So it is simply deduction over again. 
Peirce's thinking about deduction, induction, and abduction can be seen 
also  from examples he gives of arguments that are similar to the syllogisms he 
 discusses, but retain the universal affirmative judgment only for the 
Case,  using a definite percentage between 0% and 100% for both the Rule and 
the 
 Result. 
Corresponding to AAA-1 (deduction) we have the following argument:  X% of 
Ms are Ps (Rule); all Ss are  Ms (Case); therefore, X% of Ss are Ps  
(Result). Construing this argument, as we did before, as applying to drawing  
balls 
from urns, the argument becomes: X% of the balls in this urn are  red; all 
the balls in this random sample are taken from this urn; therefore,  X% of 
the balls in this random sample are red. Peirce still regards  this argument 
as being a deduction, even though it is not—as the argument AAA-1  is—a 
necesary inference. He calls such an argument a “statistical deduction” or  a “
probabilistic deduction proper.”  
Corresponding to AAA-3 (induction) we have the following argument:  X% of 
Ss are Ps (Result); all Ss are  Ms (Case); therefore, X% of Ms are Ps  
(Rule). Construing this argument as applying to drawing balls from urns, the  
argument becomes: X% of the balls in this random sample are red; all  the balls 
in this random sample are taken from this urn; therefore, X%  of the balls 
in this urn are red. Here we still have an argument whose essence  is the 
logical transition from a random sample to the population from which the  
sample is taken. The inference is made by virtue of what Hans Reichenbach 
called  
“the straight rule”: the proportion of a trait found in the sample is 
attributed  also to the population. 
Corresponding to AAA-2 (abduction) we have the following argument:  X% of 
Ms are Ps (Rule); X% of Ss  are Ps (Result); therefore, all Ss are Ms (Case). 
 Construing this argument as applying to drawing balls from urns, the 
argument  becomes: X% of the balls in this urn are red; X% of the balls  in 
this 
random sample are red; therefore, all the balls in this random sample  are 
taken from this urn. Again here we have the character of an educated guess  
or inference to a plausible explanation. 
Over many years Peirce modified his views on the three types of arguments,  
sometimes changing his views but mostly extending them by expanding his  
commentary upon the original trichotomy. Occasionally he swerved between one  
view and another concerning which larger class of arguments a particular  
instance or sub-type of argument belonged to. For example, he seemed to have  
some hesitation about whether arguments from analogy should be construed as  
inductions (arguments from a sample of the properties of things to a 
population  of the properties of things) or abductions (conjectures made on the 
basis of  sufficient similarity, which notion might not easily be analyzed in 
terms of  sets of properties). 
The most important extension Peirce made of his earliest views on what  
deduction, induction, and abduction involved was to integrate the three 
argument  forms into his view of the systematic procedure for seeking truth 
that he 
called  the “scientific method.” As so integrated, deduction, induction, 
and abduction  are not simply argument forms any more: they are three phases 
of the methodology  of science, as Peirce conceived this methodology. In 
fact, in Peirce's most  mature philosophy he virtually (perhaps totally and 
literally) equates the  trichotomy with the three phases he discerns in the 
scientific method.  Scientific method begins with abduction or hypothesis: 
because of some perhaps  surprising or puzzling phenomenon, a conjecture or 
hypothesis is made about what  actually is going on. This hypothesis should be 
such as to explain the  surprising phenomenon, such as to render the 
phenomenon more or less a matter of  course if the hypothesis should be true. 
Scientific method then proceeds to the  stage of deduction: by means of 
necessary 
inferences, conclusions are drawn from  the provisionally-adopted hypothesis 
about the obtaining of phenomena other than  the surprising one that 
originally gave rise to the hypothesis. Conclusions are  reached, that is to 
say, 
about other phenomena that must obtain if the  hypothesis should actually be 
true. These other phenomena must be such that  experimental tests can be 
performed whose results tell us whether the further  phenomena do obtain or do 
not obtain. Finally, scientific method proceeds to the  stage of induction: 
experiments are actually carried out in order to test the  
provisionally-adopted hypothesis by ascertaining whether the deduced results do 
 or do not 
obtain. At this point scientific method enters one or the other of two  “
feedback loops.” If the deduced consequences do obtain, then we loop back to  
the deduction stage, deducing still further consequences of our hypothesis and 
 experimentally testing for them again. But, if the deduced consequences do 
not  obtain, then we loop back to the abduction stage and come up with some 
new  hypothesis that explains both our original surprising phenomenon and 
any new  phenomena we have uncovered in the course of testing our first, and 
now failed,  hypothesis. Then we pass on to the deduction stage, as before. 
The entire  procedure of hypothesis-testing, and not merely that part of it 
that consists of  arguing from sample to population, is called induction in 
Peirce's later  philosophy. 
An important part of Peirce's full conception of scientific method is what 
he  called the “economics (or: economy) of research.” The idea is that, 
because  research is difficult, research labor-time is valuable and should not 
be wasted.  Both in the creation of hypotheses to be tested and in the 
experiments chosen to  test these hypotheses, we should act so as to get the 
very 
most cognitive bang  for the buck, so to say. The object is to proceed at 
every stage so as to  maximize the reduction in indeterminacy of our beliefs. 
Peirce had an elaborate,  mathematical theory of some aspects of the 
economy of research, and he published  several complex papers on this topic. 
The 
following section of the present  article contains further information on 
Peirce's notion of the economy of  research. 
4. Pragmatism, Pragmaticism, and the Scientific Method
Probably Peirce's best-known works are the first two articles in a series 
of  six that originally were collectively entitled Illustrations of the Logic 
of  Science and published in Popular Science Monthly from November  1877 
through August 1878. The first is entitled “The Fixation of Belief” and the  
second is entitled “How to Make Our Ideas Clear.” In the first of these 
papers  Peirce defended, in a manner consistent with not accepting naive 
realism, the  superiority of the scientific method over other methods of 
overcoming doubt and  “fixing belief.” In the second of these papers Peirce 
defended 
a “pragmatic”  notion of clear concepts. 
Perhaps the single most important fact to keep in mind in trying to  
understand Peirce's philosophy concerning clarity and the proper method of  
fixing 
belief is that all his life Peirce was a practicing physical scientist:  
already mentioned is the fact that he worked as a physical scientist for 32  
years in his job with the United States Coast and Geodetic Survey. As Peirce  
understood the topics of philosophy and logic, philosophy and logic were  
themselves also sciences, although not physical sciences. Moreover, he  
understood philosophy to be the philosophy of science, and he understood logic  
to be the logic of science (where the word “science” has a sense that is 
best  captured by the German word Wissenschaft). 
It is in this light that his specifications of the nature of pragmatism are 
 to be understood. It is also in this light that his later calling of his 
views  “pragmaticism,” in order to distinguish his own scientific philosophy 
from other  conceptions and theories that were trafficked under the title “
pragmatism,” is  to be understood. When he said that the whole meaning of a 
(clear) conception  consists in the entire set of its practical 
consequences, he had in mind that a  meaningful conception must have some sort 
of 
experiential “cash value,” must  somehow be capable of being related to some 
sort 
of collection of possible  empirical observations under specifiable 
conditions. Peirce insisted that the  entire meaning of a meaningful conception 
consisted in the totality of such  specifications of possible observations. For 
example, Peirce tended to spell out  the meaning of dispositional 
properties such as “hard” or “heavy” by using the  same sort of counterfactual 
constructions as, say, Karl Hempel would use. Peirce  was not a simple 
operationalist in his philosophy of science; nor was he a  simple 
verificationist in 
his epistemology: he believed in the reality of  abstractions, and in many 
ways his thinking about universals resembles that of  the medieval realists 
in metaphysics. Nevertheless, despite his metaphysical  leanings, Peirce's 
views bear a strong family resemblance to operationalism and  verificationism. 
In regard to physical concepts in particular, his views are  quite close to 
those of, say, Einstein, who held that the whole meaning of a  physical 
concept is determined by an exact method of measuring it. 
The previous point must be tempered with the fact that Peirce increasingly  
became a philosopher with broad and deep sympathies for both transcendental 
 idealism and absolute idealism. His Kantian affinities are simpler and 
easier to  understand than his Hegelian leanings. Having rejected a great deal 
in Kant,  Peirce nevertheless shared with Charles Renouvier the view that 
Kant's  (quasi-)concept of the Ding an sich can play no role whatsoever in  
philosophy or in science other than the role that Kant ultimately assigned to  
it, viz. the role of a Grenzbegriff: a boundary-concept, or, perhaps a  bit 
more accurately, a limiting concept. A supposed “reality” that is “outside”
  of every logical possibility of empirical or logical interaction with “it”
 can  play no direct role in the sciences. Science can deal only with 
phenomena, that  is to say, only with what can “appear” somehow in experience. 
All scientific  concepts must somehow be traceable back to phenomenological 
roots. Thus, even  when Peirce calls himself a “realist” or is called by 
others a “realist,” it  must be kept in mind that Peirce was always a realist 
of the Kantian “empirical”  sort and not a Kantian “transcendental realist.”
 His realism is similar to what  Hilary Putnam has called “internal realism.
” (As was said, Peirce was also a  realist in quite another sense of he 
word: he was a realist or an  anti-nominalist in the medieval sense.) 
Peirce's Hegelianism, to which he increasingly admitted as he approached 
his  most mature philosophy, is more difficult to understand than his 
Kantianism,  partly because it is everywhere intimately tied to his entire late 
theory of  signs (semeiotic) and sign use (semeiosis), as well as to his 
evolutionism and  to his rather puzzling doctrine of mind. There are at least 
four 
major  components of his Hegelian idealism. First, for Peirce the world of 
appearances,  which he calls “the phaneron,” is a world consisting entirely 
of signs. Signs  are qualities, relations, features, items, events, states, 
regularities, habits,  laws, and so on that have meanings, significances, or 
interpretations. Second, a  sign is one term in a threesome of terms that 
are indissolubly connected with  each other by a crucial triadic relation 
that Peirce calls “the sign relation.”  The sign itself (also called the 
representamen) is the term in the sign relation  that is ordinarily said to 
represent or mean something. The other two terms in  this relation are called 
the 
object and the interpretant. The object is what  would ordinarily would be 
said to be the “thing” meant or signified or  represented by the sign, what 
the sign is a sign of. The interpretant  of a sign is said by Peirce to be 
that to which the sign represents the  object. What exactly Peirce means by 
the interpretant is difficult to pin down.  It is something like a mind, a 
mental act, a mental state, or a feature or  quality of mind; at all events 
the interpretant is something ineliminably  mental. Third, the interpretant 
of a sign, by virtue of the very definition  Peirce gives of the 
sign-relation, must itself be a sign, and a sign moreover of  the very same 
object that 
is (or: was) represented by the (original) sign. In  effect, then, the 
interpretant is a second signifier of the object, only one  that now has an 
overtly mental status. But, merely in being a sign of the  original object, 
this 
second sign must itself have (Peirce uses the word  “determine”) an 
interpretant, which then in turn is a new, third sign of the  object, and again 
is 
one with an overtly mental status. And so on. Thus, if  there is any sign at 
all of any object, then there is an infinite sequence of  signs of that 
same object. So, everything in the phaneron, because it is a sign,  begins an 
infinite sequence of mental interpretants of an object. 
But now, there is a fourth component of Peirce's idealism: Peirce makes  
everything in the phaneron evolutionary. The whole system evolves. Three 
figures  from the history of culture loomed exceedingly large in the 
intellectual 
 development of Peirce and in the cultural atmosphere of the period in 
which  Peirce was most active: Hegel in philosophy, Lyell in geology, and 
Darwin 
(along  with Alfred Russel Wallace) in biology. These thinkers, of course, 
all have a  single theme in common: evolution. Hegel described an evolution 
of ideas, Lyell  an evolution of geological structures, and Darwin an 
evolution of biological  species and varieties. Peirce absorbed it all. 
Peirce's 
entire thinking, early  on and later, is permeated with the evolutionary 
idea, which he extended  generally, that is to say, beyond the confines of any 
particular subject matter.  For Peirce, the entire universe and everything in 
it is an evolutionary product.  Indeed, he conceived that even the most 
firmly entrenched of nature's habits  (for example, even those habits that are 
typically called “natural laws”) have  themselves evolved, and accordingly 
can and should be subjects of philosophical  and scientific inquiry. One can 
sensibly seek, in Peirce's view, evolutionary  explanations of the 
existence of particular natural laws. For Peirce, then, the  entire phaneron 
(the 
world of appearances), as well as all the ongoing processes  of its 
interpretation through mental significations, has evolved and is  evolving. 
Now, no one familiar with Hegel can escape the obvious comparison: we have 
in  Peirce an essentially idealist theory that is similar to the idealism 
that Hegel  puts forward in the Phaenomenologie des Geistes. Furthermore, both 
 Hegel and Peirce make the whole evolutionary interpretation of the 
evolving  phaneron to be a process that is said to be logical, the “action” of 
logic  itself. Of course there are differences between the two philosophers. 
For  example, what exactly Hegel's logic is has been shrouded in mystery for 
every  Hegelian after Hegel himself (and some philosophers, for example 
Popper, would  say for every Hegelian including Hegel). By contrast Peirce's 
logic is  reasonably clear, and he takes great pains to work it out in 
intricate 
detail;  basically Peirce's logic is the whole logical apparatus of the 
physical and  social sciences. 
One implication of the unending nature of the interpretation of appearances 
 through infinite sequences of signs is that Peirce cannot be any type of  
epistemological foundationalist or believer in absolute or apodeictic 
knowledge.  He must be, and is, an anti-foundationalist and a fallibilist. From 
his earliest  to his latest writings Peirce opposed and attacked all forms of 
epistemological  foundationalism and in particular all forms of Cartesianism 
and a  priorism. Philosophy must begin wherever it happens to be at the 
moment, he  thought, and not at some supposed ideal foundation, especially not 
in some world  of “private references.” The only important thing in 
thinking scientifically to  apply the scientific method itself. This method he 
held 
to be essentially public  and reproducible in its activities, as well as 
self-correcting in the following  sense: No matter where different researchers 
may begin, as long as they follow  the scientific method, their results 
will eventually converge toward the same  outcome. (The pragmatic, or 
pragmaticistic, conception of meaning implies that  two theories with exactly 
the 
same empirical content must have, despite  superficial appearances, the same 
meaning.) This ideal point of convergence is  what Peirce means by “the truth,”
 and “reality” is simply what is meant by “the  truth.” That these 
Peircean notions of reality and truth are inherently idealist  rather than 
naively 
realist in character should require no special pleading. 
Connected with Peirce's anti-foundationalism is his insistence on the  
fallibility of particular achievements in science. Although the scientific  
method will eventually converge to something as a limit, nevertheless at any  
temporal point in the process of scientific inquiry we are only at a 
provisional  stage of it and cannot ascertain how far off we may be from the 
limit to 
which  we are somehow converging. This insistence on the fallibilism of 
human inquiry  is connected with several other important themes of Peirce's 
philosophy. His  evolutionism has already been discussed: fallibilism is 
obviously connected with  the fact that science is not shooting at a fixed 
target 
but rather one that is  always moving. What Peirce calls his “tychism,” 
which is his anti-deterministic  insistence that there is objective chance in 
the world, is also intimately  connected to his fallibilism. (Tychism will be 
discussed below.) Despite  Peirce's insistence on fallibilism, he is far 
from being an epistemological  pessimist or sceptic: indeed, he is quite the 
opposite. He tends to hold that  every genuine question (that is, every 
question whose possible answers have  empirical content) can be answered in 
principle, or at least should not be  assumed to be unanswerable. For this 
reason, one his most important dicta, which  he called his first principle of 
reason, is “Do not block the way of  inquiry!” 
For Peirce, as we saw, the scientific method involves three phases or 
stages:  abduction (making conjectures or creating hypotheses), deduction 
(inferring what  should be the case if the hypotheses are the case), and 
induction 
(the testing  of hypotheses). The process of going through the stages should 
also be carried  out with concern for the economy of research. Peirce's 
understanding of  scientific method, then, is not very different from the 
standard idea of  scientific method (which, indeed, perhaps itself derived 
historically from the  ideas of William Whewell and Peirce) as being the method 
of 
constructing  hypotheses, deriving consequences from these hypotheses, and 
then experimentally  testing these hypotheses (guided always by the 
economics of research). Also, as  was said above, Peirce increasingly came to 
understand his three types of  logical inference as being phases or stages of 
the 
scientific method. For  example, as Peirce came to extend and generalize his 
notion of abduction,  abduction became defined as inference to and 
provisional acceptance of an  explanatory hypothesis for the purpose of testing 
it. 
Abduction is not always  inference to the best explanation, but it is always 
inference to some  explanation or at least to something that clarifies or 
makes routine some  information that has previously been “surprising,” in 
the sense that we would  not have routinely expected it, given our 
then-current state of knowledge.  Deduction came to mean for Peirce the drawing 
of 
conclusions as to what  observable phenomena should be expected if the 
hypothesis is correct. Induction  came for him to mean the entire process of 
experimentation and interpretation  performed in the service of hypothesis 
testing. 
A few further comments are perhaps in order in connection with Peirce's 
idea  of the economy (or: the economics) of research. Concern for the economy 
of  research is a crucial and ineliminable part of Peirce's idea of the 
scientific  method. He understood that science is essentially a human and 
social 
enterprise  and that it always operates in some given historical, social, 
and economic  context. In such a context some problems are crucial and 
paramount and must be  attended-to immediately, while other problems are 
trivial or 
frivolous or at  least can be put off until later. He understood that in 
the real context of  science some experiments may be vitally important while 
others may be  insignificant. Peirce also understood that the economic 
resources of the  scientist (time, money, ability to exert effort, etc.) are 
always scarce, even  though all the while the “great ocean of truth,” which 
lies 
undiscovered before  us, is infinite. All resources for carrying out 
research, such as personnel,  person-hours, and apparatus, are quite costly; 
accordingly, it is wasteful,  indeed irrational, to squander them. Peirce 
proposed, therefore, that careful  consideration be paid to the problem of how 
to 
obtain the biggest  epistemological “bang for the buck.” In effect, the 
economics of research is a  cost/benefit analysis in connection with states of 
knowledge. Although this idea  has been insufficiently explored by Peirce 
scholars, Peirce himself regarded it  as central to the scientific method and 
to the idea of rational behavior. It is  connected with what he called “
speculative rhetoric” or “methodeutic” (which  will be discussed below). 
5. Anti-determinism, Tychism, and Evolutionism
Against powerful currents of determinism that derived from the 
Enlightenment  philosophy of the eighteenth century, Peirce urged that there 
was not the 
 slightest scientific evidence for determinism and that in fact there was  
considerable scientific evidence against it. Always by the words “science” 
and  “scientific” Peirce understood reference to actual practice by 
scientists in the  laboratory and the field, and not reference to entries in 
scientific textbooks.  In attacking determinism, therefore, Peirce appealed to 
the 
evidence of the  actual phenomena in laboratories and fields. Here, what is 
obtained as the  actual observations (e.g. measurements) does not fit 
neatly into some one point  or simple function. If we take, for example, a 
thousand measurements of some  physical quantity, even a simple one such as 
length 
or thickness, no matter how  carefully we may do so, we will not obtain the 
same result a thousand times.  Rather, what we get is a distribution 
(often, but not always and certainly not  necessarily, something akin to a 
normal 
or Gaussian distribution) of hundreds of  different results. Again, if we 
measure the value of some variable that we  assume to depend on some given 
parameter, and if we let the parameter vary while  we take successive 
measurements, the result in general will not be a smooth  function (for 
example, a 
straight line or an ellipse); rather, it will typically  be a “jagged” 
result, to which we can at best fit a smooth function by  using some clever 
method 
(for example, fitting a regression line by the method  of least-squares). 
Naively, we might imagine that the variation and relative  inexactness of our 
measurements will become less pronounced and obtrusive the  more refined 
and microscopic are our measurement tools and procedures. Peirce,  the 
practicing scientist, knew better. What actually happens, if anything, is  that 
our 
variations get relatively greater the finer is our instrumentation and  the 
more delicate our procedures. (Obviously, Peirce would not have been the  
least surprised by the results obtained from measurements at the quantum  
level.) 
What the directly measured facts of scientific practice seem to tell us,  
then, is that, although the universe displays varying degrees of habit  (that 
is to say, of partial, varying, approximate, and statistical regularity),  
the universe does not display deterministic law. It does not directly  show 
anything like total, exact, non-statistical regularity. Moreover, the  
habits that nature does display always appear in varying degrees of 
entrenchment  
or “congealing.” At one end of the spectrum, we have the nearly law-like  
behavior of larger physical objects like boulders and planets; but at the 
other  end of the spectrum, we see in human processes of imagination and 
thought an  almost pure freedom and spontaneity; and in the quantum world of 
the 
very small  we see the results of almost pure chance. 
The immediate, “raw” result, then, of scientific observation through  
measurement is that not everything is exactly fixed by exact law (even if  
everything should be constrained to some degree by habit). In his earliest  
thinking about the significance of this fact, Peirce opined that natural law  
pervaded the world but that certain facets of reality were just outside the  
reach or grasp of law. In his later thinking, however, Peirce came to 
understand  this fact as meaning that reality in its entirety was lawless and 
that 
pure  spontaneity had an objective status in the phaneron. Peirce called his 
doctrine  that chance has an objective status in the universe “tychism,” a 
word taken from  the Greek word for “chance” or “luck” or “what the gods 
happen to choose to lay  on one.” Tychism is a fundamental doctrinal part of 
Peirce's mature view, and  reference to his tychism provides an added reason 
for Peirce's insisting on the  irreducible fallibilism of inquiry. For 
nature is not a static world of  unswerving law but rather a dynamic and dicey 
world of evolved and continually  evolving habits that directly exhibit 
considerable spontaneity. (Peirce would  have embraced quantum indeterminacy.) 
One possible path along which nature evolves and acquires its habits was  
explored by Peirce using statistical analysis in situations of experimental  
trials in which the probabilities of outcomes in later trials are not  
independent of actual outcomes in earlier trials, situations of so-called  “
non-Bernoullian trials.” Peirce showed that, if we posit a certain primal habit 
 
in nature, viz. the tendency however slight to take on habits however tiny, 
then  the result in the long run is often a high degree of regularity and 
great  macroscopic exactness. For this reason, Peirce suggested that in the 
remote past  nature was considerably more spontaneous than it has now become, 
and that in  general and as a whole all the habits that nature has come to 
exhibit  have evolved. Just as ideas, geological formations, and biological 
species have  evolved, natural habit has evolved. 
In this evolutionary notion of nature and natural law we have an added  
support of Peirce's insistence on the inherent fallibilism of scientific  
inquiry. Nature may simply change, even in its most entrenched fundamentals.  
Thus, even if scientists were at one point in time to have conceptions and  
hypotheses about nature that survived every attempt to falsify them, this fact  
alone would not ensure that at some later point in time these same 
conceptions  and hypotheses would remain accurate or even pertinent. 
An especially intriguing and curious twist in Peirce's evolutionism is that 
 in Peirce's view evolution involves what he calls its “agapeism.” Peirce 
speaks  of evolutionary love. According to Peirce, the most fundamental 
engine of the  evolutionary process is not struggle, strife, greed, or 
competition. Rather it  is nurturing love, in which an entity is prepared to 
sacrifice its own  perfection for the sake of the wellbeing of its neighbor. 
This 
doctrine had a  social significance for Peirce, who apparently had the 
intention of arguing  against the morally repugnant but extremely popular 
socio-economic Darwinism of  the late nineteenth century. The doctrine also had 
for 
Peirce a cosmic  significance, which Peirce associated with the doctrine of 
the Gospel of John  and with the mystical ideas of Swedenborg and Henry 
James. In Part IV of the  third of Peirce's six papers in Popular Science 
Monthly, entitled “The  Doctrine of Chances,” Peirce even argued that simply 
being 
logical presupposes  the ethics of self-sacrifice: “He who would not 
sacrifice his own soul to save  the whole world, is, as it seems to me, 
illogical 
in all his inferences,  collectively.” To social Darwinism, and to the 
related sort of thinking that  constituted for Herbert Spencer and others a 
supposed justification for the more  rapacious practices of unbridled 
capitalism, 
Peirce referred in disgust as “The  Gospel of Greed.” 
6. Synechism, the Continuum, Infinites, and  Infinitesimals
Along with Richard Dedekind and Georg Cantor, Peirce was one of the first  
scientific thinkers to argue in favor of the existence of actually infinite  
collections, and to maintain that the paradoxes that Bernard Bolzano had  
associated with the idea of infinite collections were not really 
contradictions  at all. His criterion of the difference between finite and 
infinite 
collections  was that the so-called “syllogism of transposed quantity,” which 
had been  introduced by Augustus de Morgan, constituted a deductively valid 
argument only  when applied to finite sets; as applied to infinite sets it 
was invalid. The  syllogism of transposed quantity runs as follows. We have a 
binary relation  R defined on a set S, such that the following two premises 
are  true of the relation (where the quantifications are taken over the set  
S). First, for all x there is a y such that  Rxy. Second, for all x, y, z, 
Rxz  and Ryz implies that x = y. The conclusion (of the syllogism  of 
transposed quantity) is that for all x there exists a y  such that Ryx. One of 
Peirce's favorite examples helps elucidate the  idea, even if it perhaps be not 
perfectly politically correct: Every Texan kills  some Texan; no Texan is 
killed by more than one Texan; therefore every Texan is  killed by some 
Texan. The argument's conclusion follows validly only if the set  of Texans is 
finite. 
If by Rxy in the syllogism of transposed quantity we take  f(x) = y, where 
the function is defined on and has  values in the set S, then the second 
premise of the syllogism of  transposed quantity says that f is a one-one 
function. The conclusion  says that every member of S is the image under f of 
some  member of S. Thus the syllogism of transposed quantity says that no  
one-one function can map the set S to a proper subset of itself. This  
assertion 
holds, of course, only if S is a finite set. So, as it turns  out, Peirce's 
definition of the difference between finite and infinite sets is  virtually 
equivalent to the standard one, which is found in Section 5 of Richard  
Dedekind's Was Sind und Was Sollen die Zahlen?, to the effect that an  infinite 
set is one that can be placed into a one-to-one correspondence with a  
proper subset of itself. Peirce claimed on various occasions to have reached 
his 
definition of the difference between finite and infinite collections at 
least  six years before Dedekind reached his own definition. 
Peirce held that the continuity of space, time, ideation, feeling, and  
perception is an irreducible deliverance of science, and that an adequate  
conception of such continua is an extremely important part of all the sciences. 
 
The doctrine of the continuity of nature he called “synechism,” a word 
deriving  from the Greek preposition that means “(together) with.” In 
mid-1892, somewhat  under the influence of reading Cantor's works, Peirce 
defined a 
(linear)  continuum to be a linearly-ordered infinite set C such that (1) 
for any  two distinct members of C there exists a third member of C  that is 
strictly between these; and (2) every countably infinite subset of  C that 
has an upper (lower) bound in C has a least upper bound  (greatest lower 
bound) in C. The first property he called “Kanticity”  and the second “
Aristotelicity.” (Today we would likely call these properties  “density” and “
closedness,” respectively.) The second condition has the  corollary that a 
continuum contains all its limit points, and sometimes Peirce  used this 
property 
in conjunction with “Kanticity” to define a continuum. 
Toward the end of the nineteenth century, however, Peirce began to hold 
that  Kanticity and Aristotelicity, even when conjoined, were insufficient to 
define  adequately the notion of a continuum. He maintained that he had 
framed an  updated conception of continua by somewhat loosening his attachment 
to 
Cantor's  ideas. He began to write in ways that, at least at first glance, 
seem close to  falling into Cantor's Paradox; Peirce, however, tried to 
avoid outright  contradiction by means of embracing some sort of non-standard 
idea about the  identity of points on a line. For example, in Lecture 3 of his 
Cambridge  Conferences Lectures of 1898, published as Reasoning and the 
Logic of  Things, Peirce says that if a line is cut into two portions, the 
point at  which the cut takes place actually becomes two points. What Peirce's 
new  approach is, in mathematical detail, and whether or not it contains 
hidden but  real contradictions, is a problem that has not yet been solved by 
researchers  into Peirce's logic and mathematics. 
Connected with his new conception of the continuum is Peirce's increasingly 
 frequent and sometimes pugnacious defenses of the doctrine of the reality 
of  infinitesimal quantities. The doctrine was not newly taken up by Peirce 
late in  the nineteenth century; indeed, he had held the doctrine for some 
time, and it  had been the doctrine of his father Benjamin. He considered it 
superior to the  newer doctrine of limits for providing a foundation for the 
differential and  integral calculus. What was new was that Peirce began to 
see the doctrine of  infinitesimals as the key to his updated doctrine of 
the continuum. Thus, adding  to his long-standing defense of infinitely large 
magnitudes (Peirce often used  the word “multitudes.”), Peirce began 
vigorously to defend infinitely small  magnitudes, infinitesimal magnitudes. 
Many 
examples of such defenses can be  found. Carolyn Eisele collected a number 
of such examples in her edited work  The New Elements of Mathematics by 
Charles S. Peirce. See, for example,  Volume 2, pages 169–170, where Peirce 
says “
My personal opinion is that there is  positive evidence of the real 
existence of infinitesimals; and that the  admission of them would considerably 
simplify the introduction to the calculus.”  See also Volume 3, Part 1, pages 
121–124, 125–127, 128–131, and 742–750. By the  end of the nineteenth 
century Peirce's view about infinitesimals was so rare and  remarkable that 
Josiah Royce remarked, in a footnote of his “Supplementary  Essay” for The 
World 
and the Individual, First Series, that outside of  Italy Peirce was 
virtually the only mathematical philosopher who believed in  infinitesimals. 
(See 
footnote 2, page 562 of this work by Royce.) 
Not only did Peirce defend infinitesimals. He furthermore claimed that he 
had  proved the consistency of introducing infinitesimals into the system of 
real  numbers in such a way as to form a new system in which there were 
infinitely  many entities that were not equal to zero and yet were all smaller 
than any real  number r that is not equal to zero, no matter how small r  
might be. To use modern terminology, Peirce was claiming to have shown the  
existence of ordered fields that were non-Archimedean. It was these  
non-Archimedean fields that Peirce now wanted to call genuine continua.  
Additionally, 
Peirce wanted to use his notion infinitesimal quantities and his  revised 
concept of the continuum in order to justify the traditional  pre-Gaussian 
definitions and underpinnings of the differential calculus. 
Peirce also made a number of remarks that suggest, in connection with the  
foregoing enterprise, that he had a novel conception of the topology of 
points  in a continuum. All these remarks he connected with his previous 
defenses of  infinite sets. For these reasons some Peirce scholars, and in 
particular the  great Peirce scholar Carolyn Eisele, have suggested that his 
ideas 
were an  anticipation of Abraham Robinson's non-standard analysis of 1964. 
Whether this  actually be so or not, however, is at the present time far from 
clear. Peirce  certainly says many things that are quite suggestive of the 
construction of  non-standard models of the theory of ordered fields by means 
of using  equivalence classes of countably infinite Cartesian Products of 
the standard  real numbers and then applying Loś's Theorem. However, no 
commentator up to now  has provided anything even remotely resembling a careful 
and detailed exposition  of Peirce's thinking in this area. Unfortunately, 
most of Peirce's published  writing and public talks on this topic were 
designed for audiences that were  extremely unsophisticated mathematically (a 
fact 
that he lamented). For that  reason most of what Peirce said on the topic 
is picturesque and intriguing, but  extremely obscure. The entire analysis of 
Peirce's notion of an infinitesimal,  as well as the exact bearing this 
notion has on his concept of a real continuum  and on his idea of the topology 
of the points of a continuum, still awaits  meticulous mathematical 
discussion.

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