Could the mind, as in number, come to so small a part of extension or duration as excluded divisibility, that would be, as it were, the indivisible unit or idea; by repetition of which it would make its more enlarged ideas of extension and duration. But since the mind is not able to frame an idea of any space without parts, instead thereof it makes use of the common measures, which by familiar use, in each country, have imprinted themselves on the memory (as inches and feet, or cubits and parasangs; and so seconds, minutes, hours, days, and years in duration): the mind makes use, I say, of such ideas as these, as simple ones; and these are the component parts of larger ideas, which the mind, upon occasion, makes by the addition of such known lengths which it is acquainted with. On the other side, the ordinary smallest measure we have
of extension consists in having partes extra partes (as the schools speak), it is always, in the sense of Mr. Locke, a simple idea; because the idea of having partes extra partes cannot be resolved into two other ideas. For the remainder of the objection made to Mr. Locke, with respect to the nature of extension, Mr. Locke was aware of it, as may be seen in § 9, chap. 15, of the second book, where he says, that "the least portion of space or extension, whereof we have a clear and distinct idea, may perhaps be the fittest to be considered by us as a simple idea of that kind, out of which our complex modes of space and extension are made up." So that, according to Mr. Locke, it may very fitly be called a simple idea, since it is the least idea of space that the mind can form to itself, and that cannot be divided by the mind into any less, whereof it has in itself any determined perception. From whence it follows, that it is to the mind one simple idea; and that is sufficient to take away this objection: for it is not the design of Mr. Locke, in this place, to discourse of any thing but concerning the idea of the mind. But if this is not sufficient to clear the difficulty, Mr. Locke hath nothing more to add, but that if the idea of extension is so peculiar that it cannot exactly agree with the definition that he has given of those simple ideas, so that it differs in some manner from all others of that kind, he thinks it is better to leave it there exposed to this difficulty, than to make a new division in his favour. It is enough for Mr. Locke that his meaning can be understood. It is very common to observe intelligible discourses spoiled by too much subtilty in nice divisions. We ought to put things together as well as we can, doctrinæ causâ: but, after all, several things will not be bundled up together under our terms and ways of speaking.
