An Essay Concerning Human Understanding/Book II/Chapter XXIV

1. A collective idea is one idea. Besides these complex ideas of several single substances, as of man, horse, gold, violet, apple, &c., the mind hath also complex collective ideas of substances ; which I so call, because such ideas are made up of many particular substances considered together, as united into one idea, and which so joined are looked on as one ; v.g. the idea of such a collection of men as make an army, though consisting of a great number of distinct substances, is as much one idea as the idea of a man : and the great collective idea of all bodies whatsoever, signified by the name world, is as much one idea as the idea of any the least particle of matter in it ; it sufficing to the unity of any idea, that it be considered as one representation or picture, though made up of ever so many particulars.

2. Made by the power of composing in the mind. These collective ideas of substances the mind makes, by its power of composition, and uniting severally either simple or complex ideas into one, as it does, by the same faculty, make the complex ideas of particular substances, consisting of an aggregate of divers simple ideas, united in one substance. And as the mind, by putting together the repeated ideas of unity, makes the collective mode, or complex idea, of any number, as a score, or a gross, &c., – so, by putting together several particular substances, it makes collective ideas of substances, as a troop, an army, a swarm, a city, a fleet ; each of which every one finds that he represents to his own mind by one idea, in one view ; and so under that notion considers those several things as perfectly one, as one ship, or one atom. Nor is it harder to conceive how an army of ten thousand men should make one idea, than how a man should make one idea ; it being as easy to the mind to unite into one the idea of a great number of men, and consider it as one, as it is to unite into one particular all the distinct ideas that make up the composition of a man, and consider them all together as one.

3. Artificial things that are made up of distinct substances are our collective ideas. Amongst such kind of collective ideas are to be counted most part of artificial things, at least such of them as are made up of distinct substances : and, in truth, if we consider all these collective ideas aright, as army, constellation, universe, as they are united into so many single ideas, they are but the artificial draughts of the mind ; bringing things very remote, and independent on one another, into one view, the better to contemplate and discourse of them, united into one conception, and signified by one name. For there are no things so remote, nor so contrary, which the mind cannot, by this art of composition, bring into one idea ; as is visible in that signified by the name universe.