there it exercises its sensitive faculty, as the spider in the centre of its web. The nerves of the brain push or shake it, and cause thereby that not this immediate impression, but the one which is made upon quite remote parts of the body, is represented as an object which is present outside of the brain. From this seat it moves the ropes and levers of the whole machinery, causing arbitrary movements at will. Such propositions can be proved only very superficially or not at all, and as the nature of the soul is, indeed, not well enough known, they can be just as weakly combatted. And so I do not care to join in that kind of learned dispute, in which both parties usually have most to say about that of which they know nothing. But I will follow only the conclusions to which a doctrine of this nature must lead me." In the first instance, according to the propositions so much recommended to me, my soul does not differ from any element of matter in the way in which it is present in space. Further, the power of reasoning is an internal quality which I could not perceive anyhow,
received either by hearing or sight, both of which senses are stimulated by impressions in the brain, as their organs are also next to this part. Now, if the production of these signs which Cartesius calls "ideas materiales," is properly an irritation of the nerves such as to produce a movement similar to that which formerly caused the sensation, then, in meditation, the tissue of the brain will be compelled to quiver as with the former impressions and it is chiefly the brain, therefore, that will become tired. But, if the thinking be accompanied by affections, we feel not only the brain to be taxed, but also those irritable parts which, usually, are in sympathy with the soul.
