84. That, so far as any inference from past to future uniformities is necessary to the science of nature, his doctrine does more than justify such ‘suspicion,’ is plain enough. Does it, however, leave room for so much as a knowledge of past uniformities of fact, in which the natural philosopher, accepting the doctrine, might probably seek refuge? At first sight, it might seem to do so. ‘As, when our senses are actually employed about any object, we do know that it does exist; so by our memory we may be assured that heretofore things that affected our senses have existed--and thus we have knowledge of the past existence of several things, whereof our senses having informed us, our memories still retain the ideas.’ (Book IV. chap. xi. sec. 11.) Let us see, however, how this knowledge is restricted. ‘Seeing water at this instant, it is an unquestionable truth to me that water doth exist; and remembering that I saw it yesterday, it will also be always true, and as long as my memory retains it, always an undoubted proposition to me, that water did exist the 18th of July, 1688; as it will also be equally true that a certain number of very fine colours did exist, which at the same time I saw on a bubble of that water; but being now quite out of sight both of the water and bubbles too, it is no more certainly known to me that the water doth now exist, than that the bubbles and colours therein do so; it being no more necessary that water should exist to-day because it existed yesterday, than that the colours or bubbles exist to-day because they existed yesterday.’ (_Ibid_.) Locke not aware of the full effect of his own doctrine ...