On the one hand Descartes repeatedly claims that any theories present - PDF document

1 . On the one hand, Descartes repeatedly
. On the one hand, Descartes repeatedly claims that any theories presented in science must be certain and indubitable. On the other hand, Descartes himself presents an astonishing number of speculative explanations of various scientific phenomena. In response to t

2 his tension, commentators have suggested
his tension, commentators have suggested that Descartes changed his mind about scientific theories having to be certain and indubitable, that he lacked the conceptual resources to describe the appropriate epistemic attitude towards speculative theories, or that th

3 e presence of geometrical principles in
e presence of geometrical principles in these , according to which there also exist thinking substances, or souls. Finally, a 3 Indeed, Florka (2001) argues for the stronger view that Descartes rejected synthesis al

4 together. As Florka correctly notes, Des
together. As Florka correctly notes, Descartes was suspicious of synthesis since he associated it with the syllogistic logic that he famously rejected as useless for discovering genuine knowledge. However, even Florka must acknowledge that deductions discovered by

5 analysis can be presented, as Descartes
analysis can be presented, as Descartes puts it, Òin the synthetic styleÓ (Cottingham et al. 1985b, 113), since such a presentation of the is by its very nature infinitely perfect in every way (infinitely good, infinitely powerful, infinitely knowing, etc.). We

6 can call this the principle of GodÕs inf
can call this the principle of GodÕs infinite perfection. On Descartes view, all three Ôfirst principlesÕ are self-evident and thus certain and indubitable, but DescartesÕ more interesting claim is that all natural phenomena can be deduced from them. How exactly a

7 re natural phenomena supposed to be dedu
re natural phenomena supposed to be deduced from these principles? The first step is to use the principles to deduce laws of motion for material bodies. In deducing these laws, Descartes appeals not only to the principle of extension, but also to the principle of

8 GodÕ infinite perfection. For example, D
GodÕ infinite perfection. For example, Descartes appeals to the GodÕs infinite perfection to support the claim that God is immutable, and would thus create a world in which the total amount of motion remains constant through time. This result about the total amoun

9 t of motion in the world is used as an a
t of motion in the world is used as an assumption in the deduction of the first law of motion, according to which all simple and undivided things never change unless they are acted on by external causes. In an analogous way, Descartes deduces two other laws of mot

10 ion from his first principles.5 Having
ion from his first principles.5 Having deduced these laws of motion from first principles, Descartes proceeds systematically, in part III of the Principles the observed phenomena as a guide in his scientific theorizing. So DescartesÕ mechanical theories are const

11 rained both by higher-level laws of moti
rained both by higher-level laws of motion, and by lower-level observed phenomena. However, it is evident to any attentive reader of Descartes that the laws and the phenomena do not by themselves generally rul assemblies of wheels inside, so the supreme craftsman

12 of the real world could have produced al
of the real world could have produced all that we see in several different ways. I am very happy to admit this [É] (Cottingham et al. 1985a, 289). Descartes is very happy to admit that his scientific theories may very well be mistaken. Somehow, being wrong about t

13 he mechanical theories deduced at the pe
he mechanical theories deduced at the penultimate step of a Cartesian deduction doesnÕt bother Descartes at all. Yet this is clearly in tension with his requirement of certainty, which is unambiguously expressed in the Rules, the Discourse and in the Principles th

14 emselves. Note that the requirement of c
emselves. Note that the requirement of certainty is present even in the preface to the French edition, which was written after the Latin text had already been published and so would have been a perfect opportunity for Descartes to relax or abandon the requirement.

15 Instead, as we have seen, Descartes doe
Instead, as we have seen, Descartes does the opposite. There is clearly a tension here: How can Descartes uphold his requirement of certainty and yet give so blatantly speculative explanations in the Principles to Daniel Garber (1978, 2001), Desmond Clarke (1982,

16 1992), and Helen Hattab (2009). Althoug
1992), and Helen Hattab (2009). Although I will argue that none of these commentators have resolved the tension in an entirely satisfactory manner, it seems to me that Principles. In sum, then, there seem to be strong reasons to continue to look for a better way

17 of understanding of DescartesÕ scientif
of understanding of DescartesÕ scientific project.7 We turn next to ClarkeÕs (1982, 1992) interpretation. On ClarkeÕs view, itÕs a mistake to think that Descartes required certainty of the scientific explanations that he gives in the Principles. Rather, Clarke a

18 rgues that DescartesÕ apparent claims of
rgues that DescartesÕ apparent claims of certainty concerning his scientific explanations are due to his lacking a concept of probability between absolute certainty and mere guesswork Ð a concept that is appropriate to the kind of confirmation more relevantly for

19 our purposes), Hattab claims that the p
our purposes), Hattab claims that the presence of geometrical principles in DescartesÕ demonstrations, in the Principles and elsewhere, Òguarantees the certainty of the conclusion that is demonstratedÓ (Hattab 2009, 131). Contra Garber and Clarke, Hattab thus co

20 ncludes that Descartes took himself to h
ncludes that Descartes took himself to have upheld his requirement of certaintyin the Principlesafter all (Hattab 2009, 132). While DescartesÕ requirement of certainty and his speculative explanations in the Principles. One problem is that what Hattab refers to a

21 s the ÒconclusionsÓ of DescartesÕ demons
s the ÒconclusionsÓ of DescartesÕ demonstrations are not the mechanical theories that serve as the explanantia in DescartesÕs explanations but the observed natural phenomena that serve as the explananda.9 As Garber and Clarke both emphasize, however, the tension i

22 n DescartesÕ thought between his specula
n DescartesÕ thought between his speculative explanantions and his requirement of certainty do not arise at the level of the observed explananda but at the levelof the speculative explanantia. So even if Hattab were right that the presence of geometrical principle

23 s in Cartesian demonstrations guarantees
s in Cartesian demonstrations guarantees the certainty of their conclusions (i.e. the 9 Here I am following standard philosophical usage in calling the things that do the explaining in an explanation explanans first

24 principles. This is why Descartes finds
principles. This is why Descartes finds it appropriate, in The World, to reject explanations of the properties of material bodies that appeal to scholastic forms such as heat, cold, moisture, and dryness on the grounds that Òthese qualities themselves seem to me

25 to need explanationÓ (Cottingham et al.
to need explanationÓ (Cottingham et al. 1985a, 89). This argument would be a complete non sequitur here, there is no reason not to take this assertion and its implications at face value.13 Now, one consequence of this feature of Cartesian explanations is that pe

26 rfectly good Cartesian deductions can co
rfectly good Cartesian deductions can contain steps that are not regarded as true. To see how this follows, just recall that explanations are simply the converse of deductions grounded in first principles. So if explanations can contain explanantia that are not re

27 garded as true, the steps in a Cartesian
garded as true, the steps in a Cartesian deduction can also not be regarded as true. This fits with et al. 1985a, 144). Clearly, since at most one of these Òmany different waysÓ of deducing the phenomena goes throug

28 h a theory that is regarded as true, a d
h a theory that is regarded as true, a deduction can go through steps that are colleague Smith could afford a Ferrari by suggesting that perhaps he won the lottery. This would be a correct how-possibly explanation since it lays out a possibility on which Smith wo

29 uld afford the Ferrari, even though I ma
uld afford the Ferrari, even though I may find it highly unlikely that this possibility has been actualized.17 Note also that although why-actually explanations and how-possibly explanations are distinct kinds of explanation, there is an intimate logical relations

30 hip between them in that a howpossibly e
hip between them in that a howpossibly explanation illustrates by example that a corresponding why-actually explanation could be correct. For example, having explained how it is possible for Smith to have bought a Ferrari by suggesting that perhaps he won the lott

31 ery (a how-possibly explanation), I have
ery (a how-possibly explanation), I have also proved that it could be that Smith was actually able to buy a Ferrari because he won the lottery (which would bea why-actually explanation). Now, since the distinction between why-actually and how Later in the same art

32 icle, Descartes adds that the same is tr
icle, Descartes adds that the same is true of AristotleÕs explanations in the Õ to refer to why-actually explanations, we must be mechanical Ð otherwise it could not be grounded in first principles. For example, th

33 e explanations in terms of thingsÕ occul
e explanations in terms of thingsÕ occult powers given by the Schoolmen will not do, because they appeal to various occult powers rather than the extension of material bodies. So, while finding an explanation is in one way quite easy, it is in another way quite ha

34 rd, explanations need not be regarded a
rd, explanations need not be regarded as true, and thus need not meet Descartes stringent epistemic standards for scientific theorizing more generally. But one might still wonder what the purpose is, for Descartes, of finding scientific explanations if the theori

35 es used in such explanations are not to
es used in such explanations are not to be regarded as true. For if the theories that Descartes proposes to explain such phenomena do not meet the epistemic standards Descartes set for himself, it is hard to see why Descartes would have spent so much time giving s

36 uch explanations in the Principles. What
uch explanations in the Principles. What value, if any, is there in giving mechanical explanations for natural phenomena if these explanations are bound to give us only the uncertain knowledge that Descartes explicitly claims we should reject?20 The answer is tha

37 t Cartesian explanations have epistemic
t Cartesian explanations have epistemic value that is independent of the epistemic value of the mechanical theories that figure in such explanations. In short, the multitude and variety of such explanations are indicative of the explanatory power of the first prin

38 ciples. Consider, for example, the follo
ciples. Consider, for example, the following passage (and others quoted immediately below): 20 Recall here the passage from the First of all, there is considerable textual evidence for this interpretation. We have s

39 een a lot of that evidence already, scat
een a lot of that evidence already, scattered throughout this paper. Let me now draw attention to one particularly illuminating remark in the Principles second advantage of the current interpretation is that it make

40 s better sense of . In that case, Desca
s better sense of . In that case, Descartes would have to admit that there is at least one more principle Ð presumably, some kind of principle of magnetism Ð governing natural phenomena. On the current interpretation, the main purpose of discussing all these phen

41 omena is, simply enough, to show Descart
omena is, simply enough, to show DescartesÕ scholastic opponents that mechanical the Principles Acknowledgements I am very grateful to Alan Nelson for encouragement and very helpful feedback on an Garber, Daniel (1993). ÒDescartes and Experiment in the Discourse