The discussion regarding "primitive truths," axioms, and maxims, as well as the distinction between truths of fact and of reason, has its most important bearing in Locke's next chapter. This chapter has for its title the "Extent of Human Knowledge," and in connection with the sixth chapter, upon universal propositions, and with the seventh, upon axioms, really contains the gist of the treatment of knowledge. It is here also that are to be considered chapters three and six of book third, having respectively as their titles, "Of General Terms," and "Of the Names of Substances." To understand Locke's views upon the extent and limitations of our knowledge, it is necessary to recur to his theory of its origin. If we compare what he says about the origin of ideas from sensations with what he says about the development of general knowledge from particular, we shall find that Locke unconsciously puts side by side two different, and even contradictory, theories upon this point. In the view already given when treating of sensation, knowledge originates from the combination, the addition, of the simple ideas furnished us by our senses. It begins with the simple, the unrelated, and advances to the complex. But according to the doctrine which he propounds in treating of general terms, knowledge begins with the individual, which is already qualified by definite relations, and hence complex, and proceeds, by abstracting some of these qualities, towards the simple. Or, in Locke's own language, "ideas become general by separating from them the circumstances of time and place and any other ideas that may _determine_ them to this and that particular existence." And, still more definitely, he says that general ideas are framed by "leaving out of the _complex_ idea of individuals that which is peculiar to each, and retaining only what is common to them all." From this it follows that "general and universal belong not to the real existence of things, but are the inventions and creatures of the understanding." "When we quit particulars, the generals that rest are only creatures of our own making. . . . The signification they have is nothing but a relation that by the mind of man is added to them." And in language which reminds us of Kant, but with very different bearing, he says that relations are the workmanship of the understanding. The abstract idea of what is common to all the members of the class constitutes "nominal essence." This nominal essence, not being a particular existence in nature, but the "workmanship of the understanding," is to be carefully distinguished from the real essence, "which is the being of anything whereby it is what it is." This real essence is evidently equivalent to the unknown "substance" of which we have heard before. "It is the real, internal, and unknown constitution of things." In simple or unrelated ideas and in modes the real and the nominal essence is the same; and hence whatever is demonstrated of