Reasons and God Descartes and Beyond Founders of Modern Philosophy Lecture 3

“Suppose, said Galileo, that you drop two unequal balls from the tower at the same time. And suppose that Aristotle is right - suppose that the heavy ball falls faster, so that it steadily gains on the light ball, and hits the ground first. Very well. Now imagine the same experiment done again, with only one difference: this time the two unequal balls are joined by a string between them. The heavy ball will again move ahead, but now the light ball holds it back and acts as a drag or brake.

... So the light ball will be speeded up and the heavy ball will be slowed down; they must reach the ground together because they are tied together, but they cannot reach the ground as quickly as the heavy ball alone. Yet the string between them has turned the two balls into a single mass which is heavier than either ball - and surely - (according to Aristotle) this mass should therefore move faster than either ball?...

... Galileo’s imaginary experiment has uncovered a contradiction; he says trenchantly, ‘You see how, from your assumption that a heavier ball falls more rapidly than a lighter one, I infer that a still heavier body falls more slowly.’ There is only one way out of the contradiction; the heavy ball and the light ball must fall at the same rate, so that they go on falling at the same rate when they are tied together.” - Jacob Bronowski, “The Reach of Imagination”

P1Heavier objects fall faster than lighter ones. P2*Let there be two weights, A and B, weighing X and X-k, respectively. C1A will fall faster than B. (P1, P2) P3*Let A and B be tied together to form C, weighing 2X-k. C2C will fall slower than B (because A will be acting as a brake). (P1, P2, P3, C1) C3C will fall faster than B (because C weighs more than B). (P1, P2, P3, C1) C4C cannot fall both faster and slower than B (non-identity of discernables.) C5P1 must be false. (It is reduced to absurdity.)

“Now, from the mere fact that I know for certain that I exist and that I cannot see anything else that belongs necessarily to my nature and existence except that I am a thinking thing, I rightly conclude that my essence consists in this alone, that I am a thinking thing, a substance whose whole nature or essence is to think... - Descartes, “Sixth Meditation”

But consider this argument: P1 I cannot doubt that Batman is Batman P2 I can doubt that Batman is Bruce Wayne C1 Therefore, it is possible that Batman isn’t Bruce Wayne.

Or this argument: P1 I can doubt that ( x = ). C1 Therefore, it is possible that P1 is false.

Descartes wants to say there is an alternative route - one that runs not through the senses.

Let me explain that a little bit further:

As any eight year old child will tell you: if you card looks like this, you don’t know whodunnit, where, and with what.

“The Ghost in the Machine”

I shall begin by stating Aquinas's First Way (roughly following the Summa contra Gentiles I, 13). Since my present topic has nothing to do with the existence of God, I shall keep my commentary on the original ‘proofs’ as short as possible. Thus Aquinas: Everything that is moved, is moved by another. That some things are in motion is evident from the senses: for example, the sun. So we must either proceed to infinity, or arrive at some unmoved mover. But it is not possible (in this) to proceed to infinity. Hence there is an unmoved mover. And Aquinas continues: In this proof, two propositions themselves need proof; namely, that whatever is moved, is moved by another, and that in movers and things moved, one cannot proceed to infinity.

In commentary on Aquinas it has often been pointed out, one, that he is not restricting motion here to ‘local motion’ but is thinking of any kind of change, such as heating or becoming wet; and two, that he need not be understood as denying the possibility of an infinite past. Indeed, he says quite explicitly that the fact that the world has a beginning in time cannot be demonstrated. It is rather a regress in causation of movement or change that he denies; so if the causal order has no beginning, then it as a whole needs to have a cause. As Paley said about his watch: if we found that it included a mechanism for the production of further watches, and hence was likely to be the offspring of a long line of heath-dwelling clocks, this would only increase our admiration for the genius of the watchmaker.

In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that, for anything I knew to the contrary, it had lain there forever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer I had before given, that for anything I knew, the watch might have always been there. (...) There must have existed, at some time, and at some place or other, an artificer or artificers, who formed [the watch] for the purpose which we find it actually to answer; who comprehended its construction, and designed its use. (...) Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater or more, and that in a degree which exceeds all computation. - Paley

All this strikes us, nevertheless, as rather naïve, for we have learned to live with a great deal of scepticism, not only for the need to postulate causes but with respect to the very notion of causation. However, when we consider the reality of the theoretical entities of science, we see that their relation to the order of nature is a much more sophisticated one. For their existence is postulated to explain the regularities in nature. And if causation is one of the less respected and less studied notions in contemporary philosophy of science, explanation is a subject of the liveliest interest. So I argue: Everything that is to be explained, is to be explained by something else.