Upon the origin and nature of desires Leibniz has much more to say than about the impulses. His account of the transition from impulse to desire is based upon the conception of unconscious ideas. Slight and imperceptible impulses are working upon us all the time. Indeed, they are a necessity; for the actual state of a soul or monad at any time is, of course, one of incompleteness. Our nature must always work to free itself from its hindrances and obtain its goal of complete development. But it will not do this unless there is some stimulus, some solicitation to induce it to overcome its limitation. There is found accordingly in our every condition a feeling of dissatisfaction, or, using Locke's word, of "uneasiness;" and it is this which calls forth that activity which brings about a nearer approach to the soul's real good. But Leibniz differs from Locke in saying that this feeling of uneasiness is not a distinct, or even in most cases a conscious, one. It is not pain, although it differs from pain only in degree. Uneasiness and pain are related to each other as appetite for food is to hunger,--the first suffices to stimulate us to satisfaction, but if the want is not met, results in actual pain; if met, these "half pains" become tributary to pleasure itself. These unconscious stimuli to action result in actions which meet the want, and the aggregation of these satisfactions results in pleasure. In Leibniz's own words:-- "If these elements of pain were themselves true pains, we should always be in a state of misery, even in pursuing the good. But since there is always going on a summation of minute successes in overcoming these states of uneasiness, and these put us more and more at ease, there comes about a decided pleasure, which often has greater value even than the enjoyment of the good. Far, then, from regarding this uneasiness as a thing incompatible with happiness, I find that it is an essential condition of our happiness. For this does not consist in perfect possession, which would make us insensible and stupid, but in a constant progress towards greater results, which must always be accompanied, accordingly, by this element of desire or uneasiness."