Although the credit for setting the stage for this scholastic-Aristotelian philosophy dominant at Descartes’ time should go to Thomas Aquinas (because of his initial, thorough interpretation and appropriation of Aristotle’s philosophy), it is also important to bear in mind that other thinkers working within this Aristotelian framework such as Duns Scotus, William of Ockham, and Francisco Suarez, diverged from the Thomistic position on a variety of important issues.
Indeed, by Descartes’ time, scholastic positions divergent from Thomism became so widespread and subtle in their differences that sorting them out was quite difficult.
A criticism of the traditional employment of substantial forms and their concomitant final causes in physics is found in the But what makes it especially clear that my idea of gravity was taken largely from the idea I had of the mind is the fact that I thought that gravity carried bodies toward the centre of the earth as if it had some knowledge of the centre within itself (AT VII 442: CSM II 298).
On this pre-Newtonian account, a characteristic goal of all bodies was to reach its proper place, namely, the center of the earth.
This confusion led people to mistakenly ascribe mental properties like knowledge to entirely non-mental things like stones, plants, and, yes, even non-human animals.
The real distinction of mind and body can then also be used to alleviate this confusion and its resultant mistakes by showing that bodies exist and move as they do without mentality, and as such principles of mental causation such as goals, purposes (that is, final causes), and knowledge have no role to play in the explanation of physical phenomena.
So, the answer to the question, “Why do stones fall downward? Yet, since stones are inanimate bodies without minds, it follows that they cannot know anything at all—let alone anything about the center of the earth. 'substantial forms' which I had previously held were ones which I had put together or constructed from those basic ideas (AT VII 442-3: CSM II 298).
” would be, “Because they are striving to achieve their goal of reaching the center of the earth.” According to Descartes, this implies that the stone must have knowledge of this goal, know the means to attain it, and know where the center of the earth is located. Descartes continues on to make the following point: But later on I made the observations which led me to make a careful distinction between the idea of the mind and the ideas of body and corporeal motion; and I found that all those other ideas of . Here, Descartes is claiming that the concept of a substantial form as part of the entirely physical world stems from a confusion of the ideas of mind and body.
So the real distinction of mind and body also serves the more scientifically oriented end of eliminating any element of mentality from the idea of body.
In this way, a clear understanding of the geometrical nature of bodies can be achieved and better explanations obtained.