Editing René Descartes (section)

===Physiology and psychology===
In ''The Passions of the Soul'', published in 1649,<ref>{{Cite web|title=17th and 18th Century Theories of Emotions > Descartes on the Emotions (Stanford Encyclopedia of Philosophy)|url=https://plato.stanford.edu/entries/emotions-17th18th/LD2Descartes.html#PasMedFre|access-date=29 July 2021|website=The Stanford Encyclopedia of Philosophy|archive-date=3 September 2006|archive-url=https://web.archive.org/web/20060903001831/https://plato.stanford.edu/entries/emotions-17th18th/LD2Descartes.html#PasMedFre|url-status=live}}</ref> Descartes discussed the common contemporary belief that the human body contained animal spirits. These animal spirits were believed to be light and roaming fluids circulating rapidly around the nervous system between the brain and the muscles. These animal spirits were believed to affect the human soul, or passions of the soul. Descartes distinguished six basic passions: wonder, love, hatred, desire, joy and sadness. All of these passions, he argued, represented different combinations of the original spirit, and influenced the soul to will or want certain actions. He argued, for example, that fear is a passion that moves the soul to generate a response in the body. In line with his dualist teachings on the separation between the soul and the body, he hypothesized that some part of the brain served as a connector between the soul and the body and singled out the [[pineal gland]] as connector.<ref>{{Cite book|title= A History of Psychology: A Global Perspective: A Global Perspective|author=Eric Shiraev |publisher= Sage|year=2010 |isbn=978-1-4129-7383-0|page=86}}</ref> Descartes argued that signals passed from the ear and the eye to the pineal gland, through animal spirits. Thus different motions in the gland cause various animal spirits. He argued that these motions in the pineal gland are based on God's will and that humans are supposed to want and like things that are useful to them. But he also argued that the animal spirits that moved around the body could distort the commands from the pineal gland, thus humans had to learn how to control their passions.<ref name="Eric Shiraev 2010 87">{{Cite book|title= A History of Psychology: A Global Perspective: A Global Perspective|author=Eric Shiraev |publisher= Sage|year=2010 |isbn=978-1-4129-7383-0|page=87}}</ref>

Descartes advanced a theory on automatic bodily reactions to external events, which influenced 19th-century [[reflex]] theory. He argued that external motions, such as touch and sound, reach the endings of the nerves and affect the animal spirits. For example, heat from fire affects a spot on the skin and sets in motion a chain of reactions, with the animal spirits reaching the brain through the central nervous system, and in turn, animal spirits are sent back to the muscles to move the hand away from the fire.<ref name="Eric Shiraev 2010 87"/> Through this chain of reactions, the automatic reactions of the body do not require a thought process.<ref name="Eric Shiraev 2010 88"/>

Above all, he was among the first scientists who believed that the soul should be subject to scientific investigation. He challenged the views of his contemporaries that the soul was [[Divinity|divine]], thus religious authorities regarded his books as dangerous.<ref>{{Cite journal |last=Goudriaan |first=Aza |date=3 September 2020 |title=The Concept of Heresy and the Debates on Descartes' Philosophy |journal=Church History and Religious Culture |volume=100 |issue=2–3 |pages=172–86 |doi=10.1163/18712428-10002001 |s2cid=225257956 |issn=1871-241X |doi-access=free }}</ref> Descartes's writings went on to form the basis for theories on [[emotion]]s and how [[Cognition|cognitive]] evaluations were translated into affective processes. Descartes believed the brain resembled a working machine and that mathematics, and mechanics could explain complicated processes in it.<ref>{{cite web | url=https://www.britannica.com/biography/Rene-Descartes/Physics-physiology-and-morals | title=René Descartes - Philosophy, Mathematics, Science &#124; Britannica | date=22 August 2024 }}</ref> In the 20th century, [[Alan Turing]] advanced [[computer science]] based on [[Mathematical and theoretical biology|mathematical biology]] as inspired by Descartes. His theories on reflexes also served as the foundation for advanced [[Physiology|physiological theories]], more than 200 years after his death. The physiologist [[Ivan Pavlov]] was a great admirer of Descartes.<ref>{{Cite book|title= A History of Psychology: A Global Perspective|author=Eric Shiraev |publisher= Sage|year=2010 |isbn=978-1-4129-7383-0|page=88}}</ref>