All modes of thought have God for a cause in so far as He is a thinking thing, and not in so far as He is manifested by any other attribute. That which determines the mind to thought, therefore, is a mode of thought and not of extension, that is to say, it is not the body. Again, the motion and rest of the body must be derived from some other body, which has also been determined to motion or rest by another, and, absolutely, whatever arises in the body must arise from God, in so far as He is considered as affected by some mode of extension, and not in so far as He is considered as affected by any mode of thought, that is to say, whatever arises in the body cannot arise from the mind, which is a mode of thought. Therefore, the body cannot determine the mind to thought, neither can the mind determine the body to motion nor rest, nor to anything else, if there be anything else. This proposition will be better understood from what has been said, that is to say, that the mind and the body are one and the same thing, conceived at one time under the attribute of thought, and at another under that of extension. For this reason, the order or concatenation of things is one, whether nature be conceived under this or under that attribute, and consequently the order of the actions and passions of our body is coincident in Nature with the order of the actions and passions of the mind. Although these things are so, and no ground for doubting remains, I scarcely believe, nevertheless, that, without a proof derived from experience, men will be induced calmly to weigh what has been said, so firmly are they persuaded that, solely at the bidding of the mind, the body moves or rests, and does a number of things which depend upon the will of the mind alone, and upon the power of thought. For what the body can do no one has hitherto determined, that is to say, experience has taught no one hitherto what the body, without being determined by the mind, can do and what it cannot do from the laws of Nature alone, in so far as Nature is considered merely as corporeal. For no one as yet has understood the structure of the body so accurately as to be able to explain all its functions, not to mention the fact that many things are observed in brutes which far surpass human sagacity, and that sleep-walkers in their sleep do very many things which they dare not do when awake; all this showing that the body itself can do many things from the laws of its own nature alone at which the mind belonging to that body is amazed.