Page:Essays on the Principles of Human Action (1835).djvu/191

 supposed to be a particular object, and its whiteness is supposed to be perceived by the mind as a simple sensible quality. If, on the contrary, several such slabs of marble are presented to the mind, this is commonly considered as producing a general idea of marble and of whiteness. But this idea of whiteness, not as a quality of a particular thing, but as a common quality of different things, is rejected by the moderns as implying the supposition, that several different ideas can coalesce in the same general notion, which amounts, they say, to the contradiction, that a thing may be the same, and different at the same time. Now I would affirm whatever there is absurd or inconceivable in this latter case applies equally to the former. For what possible idea can any man form of a slab of white marble, in any other way than that of abstraction? Is the idea of its whiteness as a sensible quality the idea of a point? Is it one single impression? This Berkeley and others deny, for they say there can be no idea of colour without extension, or of quality without quantity. If there are in this object several impressions of colour, I would ask are they all distinctly perceived? Are they all the same? Or if not, are all their differences perceived by the mind, before it possibly can be impressed with the general idea of a certain sensible quality, or that the object before it is white? Is the mind aware of even the slightest stain in this object, of everything that may happen to vary it? Yet, if the idea falls any thing short of this minute and perfect knowledge, it can only be an imperfect and general notion. That is, a number of differences must be massed together in a common feeling of likeness, and a number of separate parts make up the idea of a given object. Yet this is all that is implied in forming the ideas of whiteness in general, as belonging to several objects, or