Editing Discourse on the Method (section)

=== Part V: Physics, the heart, and the soul of man and animals ===
Descartes briefly sketches how in an unpublished treatise (published posthumously as ''[[The World (book)|Le Monde]]'') he had laid out his ideas regarding the laws of nature, the sun and stars, the moon as the cause of "ebb and flow" (meaning the [[tide]]s), gravitation, light, and heat. Describing his work on light, he states:

{{Blockquote|[I] expounded at considerable length what the nature of that light must be which is found in the sun and the stars, and how thence in an instant of time it traverses the immense spaces of the heavens.|author=|title=|source=}}

His work on such physico-mechanical laws is, however, framed as applying not to our world but to a theoretical "new world" created by God

{{Blockquote|somewhere in the imaginary spaces [with] matter sufficient to compose&nbsp;... [a "new world" in which He]&nbsp;... agitate[d] variously and confusedly the different parts of this matter, so that there resulted a chaos as disordered as the poets ever feigned, and after that did nothing more than lend his ordinary concurrence to nature, and allow her to act in accordance with the laws which he had established.}}

Descartes does this "to express my judgment regarding&nbsp;... [his subjects] with greater freedom, without being necessitated to adopt or refute the opinions of the learned." (Descartes' hypothetical world would be a [[deistic]] universe.)

He goes on to say that he "was not, however, disposed, from these circumstances, to conclude that this world had been created in the manner I described; for it is much more likely that God made it at the first such as it was to be." Despite this admission, it seems that Descartes' project for understanding the world was that of re-creating creation—a cosmological project which aimed, through Descartes' particular brand of experimental method, to show not merely the possibility of such a system, but to suggest that this way of looking at the world—one with (as Descartes saw it) no assumptions about God or nature—provided the only basis upon which he could see knowledge progressing (as he states in Book II).

Thus, in Descartes' work, we can see some of the fundamental assumptions of modern cosmology in evidence—the project of examining the historical construction of the universe through a set of quantitative laws describing interactions which would allow the ordered present to be constructed from a chaotic past.

He goes on to the motion of the blood in the heart and arteries, endorsing the findings of "a physician of England" about the circulation of blood, referring to [[William Harvey]] and his work ''De motu cordis'' in a marginal note.{{sfnp|Descartes|1637}}{{rp|[http://gallica.bnf.fr/ark:/12148/btv1b86069594/f55.image 51]}} But then he disagrees strongly about the function of the heart as a pump, ascribing the motive power of the circulation to heat rather than muscular contraction.<ref>[[W. Bruce Fye]]: ''Profiles in Cardiology – René Descartes'', [http://onlinelibrary.wiley.com/doi/10.1002/clc.4960260112/pdf Clin. Cardiol. 26, 49–51 (2003)], Pdf 58,2 kB.</ref> He describes that these motions seem to be totally independent of what we think, and concludes that our bodies are separate from our [[soul]]s.

He does not seem to distinguish between [[mind]], [[Spirit (animating force)|spirit]], and soul, all of which he identifies with our faculty for rational thinking. Hence the term [[Cogito ergo sum|"I think, therefore I am."]]  All three of these words (particularly "mind" and "soul") can be signified by the single French term ''âme''.