Scientific Understanding: Philosophical Perspectives

4. Ontological Principles and the Intelligibility of Epistemic Activities

4 Ontological Principles and the Intelligibility of Epistemic Activities H a S o k C H a n g L My main goal in this essay is to establish intelligibility as an epistemic virtue that is meaningful and desirable independently of any connection it might or might not have with truth.1 In brief, my argument is that intelligibility consists of a kind of harmony between éour ontological conceptions and our epistemic activities. I will modify and broaden that formulation in the course of the discussion. I will start with an example to illustrate briefly the direction of my thinking. After that, I will make a more careful consideration of the nature of intelligibility . Then I will finish with some brief reflections on the implication of this concept of intelligibility for our understanding of scientific understanding. I will be building on an earlier article (Chang 2001), in which I tried to reformulate scientific realism as a search for intelligibility rather than truth. Although the subject of the present essay is not realism, some aspects of that earlier article are quite pertinent to the discussion of intelligibility. The discussion of intelligibility here constitutes the rudiments of a much larger philosophical project, which I call “epistemic humanism.” The first part of the project is to reach a full phenomenological understanding of direct human epistemic experience. The second part is to understand other aspects of knowledge as metaphorical extensions of the direct human experience. The explicit focus on the human is intended to combat the prevalence of alienating abstractions in today’s analytic philosophy. 64 hasok chang de Regt Txt•.indd 64 9/8/09 11:26:58 AM 65 Leibniz as an Inspiration (and a Ladder to Be Kicked Away) In my earlier work (Chang 2001), I noted some historical cases in which realist scientists such as Albert Einstein, Humphry Davy, and Gottfried Wilhelm Leibniz rejected even empirically adequate scientific theories because they considered them absurd or unintelligible. Here I will rehearse the case of a little-known work by Leibniz, in which he advanced a devastating critique of René Descartes’ physics;2 in particular, I will focus on Leibniz’s attack on Descartes ’ laws of collision. Descartes had formulated seven rules governing the elastic collision of two bodies. Take the first two rules (illustrated in fig. 4.1): Figure 4.1. Descartes’ two rules of collisions. Rule 1: if these two bodies (for example, B and C) were exactly equal [in size] and moved with an equal velocity towards one another, then they would rebound equally, and each would return in the direction it came, without any loss of speed. Rule 2: if B were somewhat larger than C, and if they met each other at the same speed, then C would be the only one to rebound in the C C C C B B B B Descartes’s First Rule of Collision Descartes’s Second Rule of Collision ontological principles and epistemic activities Descartes’ First Rule of Collision Descartes’ Second Rule of Collision de Regt Txt•.indd 65 9/8/09 11:26:58 AM 66 direction from which it came, and henceforth they would continue their movement in the same direction; B having more force than C, the former would not be forced to rebound by the latter. (Descartes 1644/1988, 10–11) Now, it might seem that Descartes’ second rule is patently false, and anyone can refute it empirically by doing a very simple experiment. Leibniz the metaphysician , however, chose to criticize it without recourse to experience. He put Descartes’ two rules side-by-side and asked what would happen in the limiting case in which the object approaching from the right-hand side (B in the figure) was bigger than the left-hand one (C), but the difference approached zero. According to Descartes, as long as the difference is nonzero, however small, the object coming from the right (B) should push straight through without any change in its speed, but as soon as the difference becomes zero it is bounced back in a U-turn. Leibniz (1692/1985, 57–59) thought this was a metaphysical absurdity, violating the principle of continuity: how would a continuous change in the circumstance of the experiment make such a discontinuous difference in the outcome?3 Leibniz articulated his principle of continuity at least in two places. In the Specimen Dynamicum of 1695, he stated, “If one case continually...