How can the soul of a human being, being only a thinking substance, determine the bodily spirits to produce voluntary actions? For it seems that all determination of movement is produced by the pushing of the thing being moved, by the manner in which it is pushed by that which moves it, or else by the quality and shape of the surface of the latter. Physical contact is required for the first two conditions, and extension for the third. You entirely exclude extension from your notion of the soul, and contact seems to me incompatible with an immaterial thing.
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