As far as I understand it, Descartes claimed that the pituitary is the "antenna" through which the brain and the soul communicate, and he also claimed only human beings have souls. So, how did he explain away the fact that many non-human animals also have the pituitary?

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    Did René Descartes do what is expected of and what comes naturally to - on pain of being ridiculed to death - people who make statements like "the pituitary/pineal gland is the seat of the soil"?
    – Hudjefa
    Jun 19, 2023 at 2:45
  • Just because there is an antenna does not mean that there is also a transmitter to tune in to, and the pineal gland has purely corporeal functions aside from receiving soul transmissions. To Descartes, a human is a ghost in the machine, and animals are machines without the ghost, "the souls of animals are nothing but their blood". His arguments are based on anecdotal surmises of animal behavior, lack of language in particular. Perhaps, God had a master design for both human and animal machines, and multipurposed human pineal gland for soul reception.
    – Conifold
    Jun 19, 2023 at 4:59
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    The first account of the pineal gland into the Treatise of Man is totally "mechanistic": D speaks of animal spirits. Only later, in the Dioptrics (1637), D asserts that the gland is the seat of the sensus communis and "that this gland is the principal seat of the soul, and the place in which all our thoughts are formed." Up to now, we may simply understand that animals, man included, have the gland but only man has the soul. In case of man, the glad is the place were the soul "communicate" with the body. [1/3] Jun 19, 2023 at 13:29
  • Only in The passions of the soul (1649) we have D's full account of the solu: "“We need to recognize that the soul is really joined to the whole body, and that we cannot properly say that it exists in any one part of the body to the exclusion of the others. [...] nevertheless there is a certain part of the body where it exercises its functions more particularly than in all the others. […] The part of the body in which the soul directly exercises its functions is not the heart at all, or the whole of the brain. [2/3] Jun 19, 2023 at 13:31
  • It is rather the innermost part of the brain, which is a certain very small gland situated in the middle of the brain’s substance." [3/3] Jun 19, 2023 at 13:31

2 Answers 2


Actually, it was the pineal gland that he attributed the soul to.

As for its presence in animals, he never discusses it, and therefore we can not know why he dismissed it, or even if he was aware of it.

Thomas Willis, writing of the gland shortly after Descartes' writings on it were published, simply offers its presence as a refutation of Descartes.


What in the world did Descartes know and understand about the physiology, structure, and function of the human brain? Where was his data? His evidence? He had no knowledge, no understanding, no data and no evidence on this topic and so his assertions can be dismissed without argument. They do not even rise to the level of irrelevance.

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