List, Ben, In a phone conversation with Ben Udell today I happened to mention Peirce's notion of a "leading principle" which I recall Peirce having considered important in consideration of the three inference patterns. Ben did some quick Googling and sent me P's discussion of a leading principle in Baldwin's Dictionary (I've cut and pasted that entire entry below my signature for ready reference). I then sent Ben a message responding to material in the first paragraph of the entry and a remark Peirce makes near the end of the second (not quoted in my email to Ben below):
GR to BU: I remember reading this passage several times a few years ago when I was trying to get a handle on P's notion of a leading principle. He writes: It is of the essence of reasoning that the reasoner should proceed, and should be conscious of proceeding, according to a general habit, or method, which he holds would either (according to the kind of reasoning) always lead to the truth, provided the premises were true; or, consistently adhered to, would eventually approximate indefinitely to the truth; or would be generally conducive to the ascertainment of truth, supposing there be any ascertainable truth. (CSP) So I take this to mean that the leading principle (general habit, method) which would "always lead to the truth" is that of deduction; that which "would eventually approximate indefinitely to the truth" is that of induction; and that which "would be generally conducive to the ascertainment of truth, supposing there be any ascertainable truth" would be that of abduction. The first is a "logical" or "formal" leading principle. The other two are "factual" or "material" leading principles. Is that how you read this passage? Ben's response was so interesting that I asked him if we might take this discussion on to the list and he agreed (there may be a brief delay in his responding to this message as he wanted to polish up some formatting in his original off-list email to me). Best, Gary R http://psychcentral.com/classics/Baldwin/Dictionary/defs/L3defs.htm#Leading%20Principle *Leading Principle: *Ger. *leitendes Prinzip*; Fr. *principe directeur*; Ital. *principio fondamentale*. It is of the essence of reasoning that the reasoner should proceed, and should be conscious of proceeding, according to a general habit, or method, which he holds would either (according to the kind of reasoning) always lead to the truth, provided the premises were true; or, consistently adhered to, would eventually approximate indefinitely to the truth; or would be generally conducive to the ascertainment of truth, supposing there be any ascertainable truth. The effect of this habit or method could be stated in a proposition of which the antecedent should describe all possible premises upon which it could operate, while the consequent should describe how the conclusion to which it would lead would be determinately related to those premises. Such a proposition is called the 'leading principle' of the reasoning. Two different reasoners might infer the same conclusion from the same premises; and yet their proceeding might be governed by habits which would be formulated in different, or even conflicting, leading principles. Only that man's reasoning would be good whose leading principle was true for all possible cases. It is not essential that the reasoner should have a distinct apprehension of the leading principle of the habit which governs his reasoning; it is sufficient that he should be conscious of proceeding according to a general method, and that he should hold that that method is generally apt to lead to the truth. He may even conceive himself to be following one leading principle when, in reality, he is following another, and may consequently blunder in his conclusion. From the effective leading principle, together with the premises, the propriety of accepting the conclusion in such sense as it is accepted follows necessarily in every case. Suppose that the leading principle involves two propositions, *L* and *L'*, and suppose that there are three premises, *P*, *P'*, *P''*; and let *C* signify the acceptance of the conclusion, as it is accepted, either as true, or as a legitimate approximation to the truth, or as an assumption conducive to the ascertainment of the truth. Then, from the five premises *L*,*L'*, *P, P'*, *P''*, the inference to *C* would be necessary; but it would not be so from *L*, *L'*, *P'*,*P''* alone, for, if it were, *P* would not really act as a premise at all. From *P'* and *P''* as the sole premises, *C* would follow, if the leading principle consisted of *L*, *L'*, and *P*. Or from the four premises *L'*, *P*, *P'*, *P''*, the same conclusion would follow if *L* alone were the leading principle. What, then, could be the leading principle of the inference of *C* from all five propositions *L*, *L'*, *P*, *P'*, *P''*, taken as premises? It would be something already implied in those premises; and it might be almost any general proposition so implied. Leading principles are, therefore, of two classes; and any leading principle whose truth is implied in the premises of every inference which it governs is called a 'logical' (or, less appropriately, a *formal*) leading principle; while a leading principle whose truth is not implied in the premises is called a 'factual' (or *material*) leading principle. (C.S.P. <http://psychcentral.com/classics/Baldwin/Dictionary/defs/colls.htm#csp>) [image: Gary Richmond] *Gary Richmond* *Philosophy and Critical Thinking* *Communication Studies* *LaGuardia College of the City University of New York* *C 745* *718 482-5690*
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