For the details of the deduction, which often makes very happy use of a rich store of psychological material, the reader must be referred to the more extended expositions. Here we can only cite as examples the chief among the genetic definitions. Perceptions (impressions) and consciousness are the same thing under different names. A lively sensation, in which the mind is entirely occupied, becomes attention, without the necessity of assuming an additional special faculty in the mind. Attention, by its retentive effect on the sensation, becomes memory. Double attention--to a new sensation, and to the lingering trace of the previous one--is comparison; the recognition of a relation (resemblance or difference) between two ideas is judgment; the separation of an idea from another naturally connected with it, by the aid of voluntary linguistic symbols, is abstraction; a series of judgments is reflection; and the sum total of inner phenomena, that wherein ideas succeed one another, the ego or person. All truths concern relations among ideas. The tactual idea of solidity accustoms us to project the sensations of the other senses also, to transfer them thither where they are not; hence arise the ideas of our body, of external objects, and of space. If we perceive several such projected qualities together, we refer them to a substratum--substance, which we know to exist, although not what it is. By force we mean the unknown, but indubitably existent, cause of motion. There are no indifferent mental states; every sensation is accompanied by pleasure or pain. Joy and pain give the determining law for the operation of our faculties. The soul dwells longer on agreeable sensations; without interest, ideas would pass away like shadows. The remembrance of past impressions more agreeable than the present ones is need; from this springs desire (_désir_) then the emotions of love, hate, hope, fear, and astonishment; finally, the will as an unconditional desire accompanied by the thought of its possible fulfillment. All inclinations, good and bad alike, spring from self-love. The predicates "good" and "beautiful" denote the pleasure-giving qualities of things, the former, that which is agreeable to smell and taste (and the passions), the latter, that which pleases sight, hearing, feeling (and the intellect). Morality is the conformity of our actions to laws, which men have established by convention with mutual obligations. In this way the good, which at first was the servant of the passions, becomes their lord.