Jennyfer asked:

Hello, I have a question about Descartes’ dualism. A lot of people have argued that with his dualism view comes the problem of interactionism: How can the mind have an influence on the body since it is a non-extended substance?

I was wondering how Descartes has defended his opinion when facing these criticisms. Did he consider that the union of the mind and the body (lying in pineal gland)was the reason of this interactionism? How did he explain that?
Thank you very much for your answer!

Answer by Jürgen Lawrenz

As you’re aware of his pineal gland hypothesis, you probably also know that he abandoned it, when told that dogs also possess a pineal gland. It did not seem right to him, as he had explicitly denied any form of conscious behaviour to animals. But whatever else may have been on his mind as a solution, it was no solution and, strictly speaking, that’s where his entire philosophy would have come unstuck, except for the fact that others (Spinoza, Malebranche, Leibniz et al) perceived it as a challenge.

Such a duality as Descartes proposed is, after all, highly intuitive. It is our daily experience. We tend to be a bit more graceful about it nowadays and accord intuition to animals as well. But the hard problem of how matter and non-matter can interact still leaves us between the devil and deep blue sea. Many of us (and our forefathers as well) have prematurely closed the question. In previous centuries by thinkers claiming that all matter is ultimately a derivative of the spirit; in our time by the opposite argument that all is matter and that therefore we only need to discover what kind of matter/energy equation settles Descartes’ issue.

As such problems always bring hardened dogmatists to the fore, it is appropriate to emphasise here that the Cartesian duality is not passe. It has been shoved under the carpet. Nevertheless, one prominent neurophysiologist — John Eccles, after all a Nobel Prize laureate — believed in Descartes’ proposition and spent years of research on it. Moreover, he believes to have discovered the interface where it all happens (not the pineal gland!). But this is much too complicated for a brief run-down. If you are interested, it is laid out in his book Evolution of the Brain — Creation of the Self, which I would therefore recommend for you to peruse. The section is entitled ‘The Microsite Hypothesis’ (p. 187ff in the Routledge paperback).