There are, however, other intrinsic determinations of substance, other modifications of the latter, which do not seem to involve any new or additional reality in the substance, over and above the modification itself. Such, for instance, are motion, rest, external form or figure, in bodies. These are called _modal_ accidents. They often affect not the substance itself immediately, but some absolute accident of the latter, and are hence called “accidental modes”. Those enumerated are obviously modes of the quantity of bodies. Now the appearance or disappearance of such an accident in a substance undoubtedly involves a real change in the latter, and not merely in our thought; when a body moves, or comes to rest, or alters its form, there is a change in the reality as well as in our thought; and in this sense these accidents are real and intrinsic to their substances. Yet, though we cannot say that motion, rest, shape, etc., are really identical with the body and only mentally distinct aspects of it, at the same time neither can we say that by their appearance or disappearance the body gains or loses any reality other than an accidental determination of itself; whereas it does gain something more than this when it is heated, or electrified, or increased in quantity; just as a man who acquires knowledge, or virtue, is not only really modified, but is modified by real entities which he has acquired, not having actually possessed them before. Finally, there are accidents which do not affect the substance intrinsically at all, which do not determine any real change in it, but merely give it an extrinsic denomination in relation to something outside it (60). Thus, while the _quality_ of heat is an absolute accident in a body, the _action_ whereby the latter heats neighbouring bodies is no new reality in the body itself, and produces no real change in the latter, but only gives it the extrinsic denomination of _heating_ in reference to these other bodies in which the effect really takes place. Similarly the _location_ of any corporeal substance in _space_ or in _time_ relatively to others in the space or time series—its _external_ place (_ubi_) or time (_quando_), as they are called—or the relative position of its parts (_situs_) in the place occupied by it: these do not intrinsically determine it or confer upon it any intrinsic modification of its substance. Not, indeed, that they are mere _entia rationis_, mere logical fictions of our thought. They are realities, but not realities which affect the substances denominated from them; they are accidental modes of other substances, or of the absolute accidents of other substances. Finally, the accident which we call a “_real_ relation” presupposes in its subject some absolute accident such as quantity or quality, or some real and intrinsic change determining these, or affecting the substance itself; but whether relation is itself a reality over and above such foundation, is a disputed question.