How Descartes Broke With Classical Thinking

Classical thinking had assigned different natures to different things—minerals had one nature, stars another, plants another. But Descartes discarded these distinctions and looked upon all things as being equal in nature. The mystical distinction among the natures of things thus disappeared. For example, respiration in the human body and the circulation of blood were no longer inexplicable, or virtually magic phenomena; both could now be treated in terms of extension and motion. The circulation of blood in the human body was analogous to the working of a water pump; respiration could be likened to the blowing back and forth of the wind, and so treated as motion. The concept of quantity replaced that of the inherent natures of things, and it was now possible for men to observe everything in the same way whether it was a living creature or a lump of ore.

Even though modern science has shown that Descartes’ conception that all objects were to be explained the same way was an oversimplification, we must still credit him with having made an extremely valuable contribution to the development of human thought. Classic science prior to the time of Descartes had classified things into innumerable fixed, complex, and isolated kinds, with the result that man’s efforts to understand his world were discouraged by the apparent unmanageability of the task. Descartes contribution lay in the fact that he tumbled this feudal system of knowledge, and in effect made man’s world susceptible to inquiry. Descartes contribution to method consists in using the concepts of extension and motion to account for all natural phenomena. They are easy to grasp, and the introduction of these relatively simple concepts did much to dispel the ignorance which had so long prevailed when the world was regarded as consisting of so many mysterious entities that it was useless for man to try to understand it. A conception that did so much to throw light where there had been darkness, which encouraged men to concern themselves with practical application instead of looking on their world with mystified bemusement, is no small improvement in human thinking.

The second conclusion we note is that Descartes made a clean break with the Aristotelian concept of final cause the purpose for which a thing exists, which governs all change, and which is the end toward which change is directed. Descartes discarded this concept, and asserted that there is no final cause in motion—that motion is no more than positional change of extension. The fact that now men did not need to concern themselves with the search for an unknowable final cause made more economical thought processes possible.