they must not consist of ideas put together at the pleasure of our thoughts, without any real pattern they were taken from, though we can perceive no inconsistence in such a combination.  The reason whereof is because we, knowing not what real constitution it is of substances whereon our simple ideas depend, and which really is the cause of the strict union of some of them one with another, and the exclusion of others; there are very few of them that we can be sure are or are not inconsistent in nature:  any further than experience and sensible observation reach Herein, therefore, is founded the reality of our knowledge concerning substances—­That all our complex ideas of them must be such, and such only, as are made up of such simple ones as have been discovered to co-exist in nature.  And our ideas being thus true, though not perhaps very exact copies, are yet the subjects of real (as far as we have any) knowledge of them.  Which (as has been already shown) will not be found to reach very far:  but so far as it does, it will still be real knowledge.  Whatever ideas we have, the agreement we find they have with others will still be knowledge.  If those ideas be abstract, it will be general knowledge.  But to make it real concerning substances, the ideas must be taken from the real existence of things.  Whatever simple ideas have been found to co-exist in any substance, these we may with confidence join together again, and so make abstract ideas of substances.  For whatever have once had an union in nature, may be united again.

13.  In our inquiries about Substances, we must consider Ideas, and not confine our Thoughts to Names, or Species supposed set out by Names.

This, if we rightly consider, and confine not our thoughts and abstract ideas to names, as if there were, or could be no other sorts of things than what known names had already determined, and, as it were, set out, we should think of things with greater freedom and less confusion than perhaps we do.  It would possibly be thought a bold paradox, if not a very dangerous falsehood, if I should say that some changelings, who have lived forty years together, without any appearance of reason, are something between a man and a beast:  which prejudice is founded upon nothing else but a false supposition, that these two names, man and beast, stand for distinct species so set out by real essences, that there can come no other species between them:  whereas if we will abstract from those names, and the supposition of such specific essences made by nature, wherein all things of the same denominations did exactly and equally partake; if we would not fancy that there were a certain number of these essences, wherein all things, as in moulds, were cast and formed; we should find that the idea of the shape, motion, and life of a man without reason, is as much a distinct idea, and makes as much a distinct sort of things from man and beast, as the idea of the shape of an ass with reason would be different from either that of man or beast, and be a species of an animal between, or distinct from both.