This, it may be said, is all very true for a certain class of desires, but the principle does not apply in the higher desires like the desire for knowledge. But knowledge originates only as serviceable, and primarily only serviceable knowledges are desired. We desire knowledge only so far as it is worth having, and it may be that I esteem all knowledge as worth something and so desirable. However, some knowledges are worth nothing and are never desired. Who wants to know the exact measurements of the pebbles on the road, or how many hairs are on the mane of his neighbour’s pony, or the names of all the inhabitants of Pekin? But if one thinks it would be any satisfaction to know such facts, he may desire to know them. The insatiable curiosity of children which seeks to know all such irrelevant facts hardly comes under the category of desire, but is rather instinctive hereditary impulse. It has no clear idea of a thing to be known and a desire to know it, but is only a spontaneous outburst of knowing activity which is inbred and comes from ancestral integration. There is a sensing and perceiving activity which is very intense at the questioning age, but which hardly implies the desire to know. The incessant “What’s this?” “What’s that?” is merely outcome of an instinctive impulsion to interpret environment; it is not significant of full-formed desire, there is no idea of thing to be known, of an actualization to be accomplished. If a man desires knowledge, not for his own sake, but for its own sake, desire as such really ceases, it merges into love and devotion, which are disinterested and clearly distinct as mental modes from desire. Desire is not a sentiment; and it does not properly include all impulse to actualization. For instance, the feeling for actualization merely as such, for achievement of ideal _per se_, is beyond the biologic stage of consciousness wherein desire has its chief function. The attainment of end merely for the sake of the end must be distinguished from actualizing an image for the pleasure of actualization, which thus has desire element. We know that the image of realization may act as end by compulsion, as in feeling of duty, which is thus marked off from desire as impulsion. Thus desire is but one mode of teleological emotion. But desire is emotion at unrealized good and not at unrealization in general.