The soul being distinct and different from the body, the latter can be only occasionally the cause of what it seems to produce in the former. From whence we must conclude, that the fenses are only.occasionally the source of our knowledge.
Let us therefore conclude that there are no ideas but such as are acquired: the first proceed immediately from the senses; the others are owing to experience, and increase in proportion as we become capable of reflecting.
It would be of no use to inquire into the nature of our thoughts. The first reflection we make on ourselves is sufficient to convince us, that we have no possible means of satisfying this inquiry. Every man is conscious of his thought; he distinguishes it perfectly from every thing else; he even distinguishes one thought from another ; and that is sufficient. If we go any further, we stray from a point which we apprehend so clearly, that it can never lead us into error.
If we had no motivation to be preoccupied with our sensations, the impressions that objects made on us would pass like shadows, and leave no trace. After several years, we would be the same as we were at our first moment, without having acquired any knowledge, and without having any other faculties than feeling. But the nature of our sensations does not let us remain enslaved in this lethargy. Since they are necessarily agreeable or disagreeable, we are involved in seeking the former, avoiding the latter; and the greater the intensity of difference between pleasure and pain, the more it occasions action in our souls. Thus the privation of an object that we judge necessary for our well-being, gives us disquiet, that uneasiness we call need, and from which desires are born. These needs recur according to circumstances, often quite new ones present themselves, and it is in this way that our knowledge and faculties develop.