Jon Zingale writes, in relevant part: > In modern mathematics, one encounters categories whose > `points` have an internal structure which can be more > complicated than one's initial intuition would provide. > There is a sense that what the interested physicist is doing > by exploring the duality is attempting to understand the nature > of 'physical points'. How is a physical point like a point in > Euclidean geometry? To what extent can there be a consistent > formal description which matches our knowledge of these points? > > Perhaps from some phenomenological perspective, we should > understand these physical points as founding all experience > regarding points and waves. After all, assuming the present > quantum mechanical presentation, all of the classical > experiences of wave-like nature and particle-like nature > are derived from interactions of these underlying primitive > objects.
Here, modulo reformatting for ASCII e-mail, is part of one section of one of my editorial chapters ("Functions of Structure in Mathematics and Modeling") in my widely unread edited book "Qualitative Mathematics for the Social Sciences" (Routledge, 2013; get your local libraries to order dozens!), which (at least) obliquely talks to the issues Jon raises here, and handles the issue of "more complicated than one's initial intuition" somewhat head-on (though probably pitched above the head of most of the social scientists who were the purported audience). ===begin=== ON MATHEMATICAL SPACES The preceding discussion of projective planes provides not just explicit examples of how set-theoretical definitions are used mathematically, but also many examples (there not drawn explicitly to attention) of how (parts of) such definitions can acquire or give meaning in the course of their mathematical and para-mathematical interactions with other structures (some mathematical but having definitions that remain out of attention, others in the world and definedif at allnon-mathematically). In this section I pick up just one of those dropped threads. Many mathematical structures have been called spaces (usually with some modifier) since at least the discovery of non-Euclidean geometriesnotably, the real projective plane RP2 and the real hyperbolic planeearly in the 19th century, and well before there were any set-theoretical foundations of mathematics. By mid 20th century, mathematical spaces were common not only in geometry but in algebra (vector spaces), mathematical analysis (Hilbert spaces, Banach spaces, Hardy spaces, and many other kinds of vector spaces with extra structure, as well as metric spaces and measure spaces), abstract algebra (representation spaces, prime ideal spaces), probability theory (probability spaces), mathematical physics (phase spaces), and especially topologythe quintessential mathematics of the 20th centuryin its many manifestations: point-set, combinatorial, algebraic, geometric, and differential. No single strictly mathematical property is shared by these many kinds of spaces, but mathematicians in general seem content to agree that the metaphor is broadly appropriate. Typically, when mathematicians call some mathematical structure S a space (here to be called a mathematical space in the hopes of averting confusion), they understand it to share, in some sense and to some degree, the following rather general pre-mathematical properties of the ordinary space of our daily experience. [Footnote 15: Many presuppositions are packed into the phrase the ordinary space of our daily experience and its variants, and most if not all of them are probably unjustifiably broad, particularly if daily experience is read so as to naïvely ignore or tendentiously suppress the considerable role of linguistic framings (cultural and sub-cultural, semi-permanent and evanescent) in that experience. Still, the phrase and its variants have a reasonably well delimited denotation that is widely understood (until it is examined overly closely), so I take the risk of using it here.] (1) A mathematical space is like a box that can contain other sorts of things. (2) A mathematical space is like a stage on which various events can happen (e.g., things can move) in the course of time. [Footnote 16: Somewhat confusingly, time is very often thought of as a mathematical space by mathematicians. See Chap. 10, p. 308, and Rudolph (2006a).] Properties (1) and (2) are essentially extrinsic to a candidate S for spacehood: they depend almost entirely not on what S is but on how S is used.[Footnote 17: In particular, one and the same mathematical structure S can be called a space or not depending on the use to which it is being put.] In contrast, a third general property is chiefly intrinsic. (3) A mathematical space has extent, and can (usually) be subdivided; a piece of a mathematical space, though (usually) of smaller extent, still has in its own right the quality of being a mathematical space. Naturally, the interpretation of (3) depends on the meaning given to extent, piece, etc., and in that sense it is somewhat extrinsic. What mathematicians typically try hard not to do, when calling a mathematical structure a space, is to attribute to that structure other properties of ordinary space that are not explicitly demanded by the context in which the structure is being used. Model-making scientists, be they physical, life, or social scientists, are often less fastidious when they adopt the metaphor of space for mathematical models in their own disciplines: in contrast with mathematicians, they tend to incorporate into their models not only the general properties (1)(3) of ordinary space, but also some or all of the following special properties. (4) Ordinary space has (or can have imposed upon it) metric properties, including (but not limited to) numerical measures of distance, area, volume, and other forms of extent; a mathematical space need not. (5) Ordinary space has (or can have imposed upon it) geometric properties, such as notions of straightness and curvature, convexity and concavity, collinearity, congruence, and the like; a mathematical space need not. (6) Ordinary space has properties of continuity, homogeneity (i.e., indistinguishability among locations per se) and isotropy (i.e., indistinguishability among directions per se) [Footnote 18: Or, at least, horizontal directions are (among themselves, ignoring their contents) indistinguishable in ordinary space; as Shepard (1992, p. 500) points out, gravity makes verticality salient for surface-dwellers (or rather, for those surface-dwellers that live above the nanoscale at which van der Waals forces, Brownian motion, etc., have effects much stronger than those of gravity).]; a mathematical space need not. [Footnote 19: In this connection, it is almost incredibleto a mathematician educated in the second half of the 20th centuryto read that, for instance, Bertrand Russell (1896) [i]n his first published paper [...] analyses the axioms of Euclidean geometry [...] and finds that some of the axioms are certainly true, and in particular a priori true, for their denial would involve logical and philosophical absurdities (p. 3). He classifies for instance the homogeneity of space as a priori true, the want of homogeneity and passivity is ... absurd: no philosopher has ever thrown doubt, so far as I know, on these two properties of empty space [...]. (Lakatos, 1962, p. 168; the unbracketed ellipsis points, and the italics, are Lakatoss.) Moreover, Russell (1896, p. 1) purports to come to his conclusions even though we are not concerned with the correspondence of Geometry with fact; we are concerned with Geometry simply as a body of reasoning, the conditions of whose possibility we wish to examine [...] we have to do with the conception of space in its most finished and elaborated form, after thought has done its utmost in transforming the intuitional data. Probably the best (though very difficult) course of action for the modern mathematician, incredulous in the face of what appears to be such an enormous blind spot, would be to take an appropriate modification of Stallingss advice (quoted on p. 64), and cultivate techniques leading to the abandonment of ones own mechanisms for maintaining ones own (surely numerous) blind spots.] (7) In ordinary space, a point is atomic, with no internal structure; in many important examples of mathematical spaces, each point is a complex structure in its own right. Although the policy of endowing mathematical spaces used as models with some or all of the special properties (4)(7) has often been harmless, and occasionally useful, in the natural sciences, I see no evidence that it has often been useful (and some evidence that it has sometimes been harmful) in the human sciences. In any case, mathematicians typically see the denial, to a given mathematical space, of some or all of these special propertiesespecially (7)as entirely normal, and frequently commendable. [Footnote 20: Euclids Definition 1 states that a point is that which has no parts. But, e.g., in all the definitions of RP2, at least some pointsbeing sets with two elementshave non-trivial, if meager, mereologies. A class of examples of mathematical spaces having far more radically non-atomic points than those of RP2 is that of configuration spaces of (mathematical or physical) systems of various sorts. In a configuration space, each point is a single configuration of the entire system. See Wehrle, Kaiser, Schmidt, and Scherer (2000) for an application to the dynamics of human affect thatin effectconstitutes a partial exploration of a mathematical space of schematic facial expressions consisting entirely of theoretically postulated facial muscle configurations (p. 105).] ===end=== I guess one thing not mentioned there, which occurs to me as I reread the text I quoted from Jon, is the importance of keeping in mind (if not necessarily always at the front of one's mind, that is, in active attention [<---notice the metaphorical "spatialization" inherent in the idiomatic uses of "at the front" and "in"]) that which "objects" are "underlying primitive objects" is not necessarily, and perhaps necessarily NOT, a fact about the system being modeled, but rather a fact about the model. Cheers, Lee Rudolph ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com archives back to 2003: http://friam.471366.n2.nabble.com/ FRIAM-COMIC http://friam-comic.blogspot.com/ by Dr. Strangelove