all fluctuation of its accidents; while these on the other hand have only that essentially dependent mode of being whereby they are actual only by affecting and determining some subject in which they inhere and which supports their actuality. The existence, therefore, of some accidents, which are not only really distinct but even physically separable from their substances, cannot reasonably be called into question. To deny the existence of such accidents, or, what comes to the same thing, their real distinction from substance, is to take up some one of these three equally untenable positions: that all the changes which take place within and around us are substantial changes; or, that there is no such thing as real change, all change being a mental illusion; or, that contradictory states can be affirmed of the same reality.(259) But the nature of the real distinction between accidents and substance is not in all cases so easy to determine. Nor can we discuss the question here in reference to each _summum genus_ of accident separately. Deferring to the chapter on _Relation_ the question of the distinction of this particular accident from substance and the other categories, we may confine our attention here to the distinction between substance and the three classes of accidents we have called _extrinsic denominations_, _modal_ accidents, and _absolute_ accidents respectively. “There are accidents,” writes Kleutgen,(260) “which place nothing and change nothing in the subject itself, but are ascribed to it by reason of some extrinsic thing; others, again, produce indeed in the subject itself some new mode of being, but without their existing in it as a new reality, distinct from its reality; others, finally, are themselves a new reality, and have thus a being which is proper to themselves, though this being is of course dependent on the substance. These latter alone can be _really_ distinct from the substance, in the full sense in which a real distinction is that between thing and thing. Now Cartesian philosophers have denied that there are any such accidents as those of the latter class; rejecting the division of accidents into absolute and modal, they teach that all accidents are mere _modifications_ or determinations of substance, that they consist solely of various locations and combinations of the ultimate parts of a substance, or relations of the latter to other substances.” Now all _extrinsic denominations_ of a substance do seem on analysis ultimately to resolve themselves partly into relations of the latter to other substances, and partly into modal or absolute accidents of other substances. Hence we may confine our attention here to the distinction between these two classes of accident and their connatural substances.