85. The result is that though I may enumerate a multitude of past matters-of-fact about water, I cannot gather them up in any general statement about it as a real existence. So soon as I do so, I pass from water as a real existence to its ‘nominal essence,’ _i.e._, to the ideas retained in my mind and put together in a fictitious substance, to which I have annexed the name ‘water.’ If we proceed to apply this doctrine to the supposed past matters-of-fact themselves, we shall find these too attenuating themselves to nonentity. Subtract in every case from the ‘particular existence’ of which we have ‘sensitive knowledge’ the qualification by ideas which, as retained in the mind, do not testify to a present real existence, and what remains? There is a certainty, according to Locke (Book IV. chap. xi. sec. 11), not, indeed, that water exists to-day because it existed yesterday--this is only ‘probable’--but that it has, as a past matter-of-fact, at this time and that ‘continued long in existence,’ because this has been ‘observed;’ which must mean (Book IV. chap. ii. secs. 1, 5, and 9), because there has been a continued ‘actual sensation’ of it. ‘Water,’ however, is a complex idea of a substance, and of the elements of this complex idea those only which at any moment are given in ‘actual sensation’ may be accounted to ‘really exist.’ First, then, must disappear from reality the ‘something,’ that unknown substratum of ideas, of which the idea is emphatically ‘abstract.’ This gone, we naturally fall back upon a fact of co-existence between ideas, as being a reality, though the ‘thing’ be a fiction. But if this co-existence is to be real or to represent a reality, the ideas between which it obtains must be ‘actual sensations.’ These, whatever they may be, are at least opposed by Locke to ideas retained in the mind, which only form a nominal essence. But it is the association of such nominal essence, in the supposed observation of water, with the actual sensation that alone gives the latter a meaning. Set this aside as unreal, and the reality, which the sensation reveals, is at any rate one of which nothing can be said. It cannot be a relation between sensations, for such relation implies a consideration of them by the mind, whereby, according to Locke, they must cease to be ‘real existences.’ (Book II. chap. xxv. sec. 1.) It cannot even be a single sensation _as continuously observed_, for every present moment of such observation has at the next become a past, and thus the sensation observed in it has lost its ‘actuality,’ and cannot, _as a ‘real existence_,’ qualify the sensation observed in the next. Restrict the ‘real existence,’ in short, as Locke does, to an ‘actual present sensation,’ which can only be defined by opposition to an idea retained in the mind, and at every instant of its existence it has passed into the mind and thus ceased really to exist. Reality is in perpetual process of disappearing into the unreality of thought.