On this subject, the author is a good deal puzzled with the question, how it is possible for the mind ever to confound one idea with another? It is indeed a puzzling question, but the answer which he gives to it in resolving it into a mistake of words, is very unsatisfactory. For there is no more reason why we should mistake one name or sign of an idea for another, than why we should mistake the ideas themselves. If every circumstance belonging to our ideas was necessarily clear and self-evident to the mind, the sign affixed to it, which is one of those circumstances, would be so too, and we find that in those things with which we have a thorough acquaintance, we never confound one name with another, or if we should, it does not disturb the idea, and is of no consequence. Among the second sort of complex ideas Mr. Locke classes those of substances. These, he says, are such combinations of simple ideas as are taken to represent distinct, particular things, subsisting by themselves, in which the supposed or confused idea of substance, such as it is, is always the first or chief. Thus, if to substance be joined the simple idea of a certain dull whitish colour, with certain degrees of weight, hardness, ductility and fusibility, we have the idea of lead; and a combination of the ideas of a certain sort of figure, with the power of motion, thought, and reasoning, joined to substance, make the ordinary idea of a man. Now of substances also there are two sorts of ideas; one of single substances, as they exist separately, as of a man or a sheep; the other of several of those put together, as an army of men or a flock of sheep: which collective ideas of several substances are as much each of them one single idea as that of a man or an unit.’ He then adds, ‘and the third sort of complex ideas is that which we call relative, which consists in the consideration and comparing one idea with another.’ This last sort of ideas seems to me the only ones that are perfectly simple and indivisible: things themselves are always complex. Mr. Locke considers rightly that we know nothing of the nature of substance, and that we can only define it as an abstract idea of some thing, that supports accidents or connects different sensible qualities together. For this modest confession of his own ignorance he was however called to a very severe account by the learned of the time, Bishop Stillingfleet and others, who thought they knew more of the matter, and could penetrate the essence of things. The ‘Essay on the Human Understanding’ is swelled out with repeated and long extracts from this controversy, and they are not the least valuable part of the work, as they show to what shifts men can be driven, to defend systematically not truth but their own opinion, who become blind and obstinate by implicit faith, and who by adhering to every established prejudice drive others into all the absurdities of paradox.