Hence, _in the order of our experience_ the first, _implicit_ notion of substance is that of “something existing in itself” (οὐσία); the first _explicit_ notion of it, however, is that by which it is apprehended as “a subject or support of accidents” (ὑποκείμενον, _sub-stare_, _substantia_); then by reflection we go back to the _explicit_ notion of it as “something existing in itself”. In the _real_ or _ontological_ order the perfection of “existing in itself” is manifestly more fundamental than that of “supporting accidents”. It is in accordance with a natural law of language that we name things after the properties whereby they reveal themselves to us, rather than by names implying what is more fundamental and essential in them. “To exist in itself” is an absolute perfection, essential to substance; “to support accidents” is only a relative perfection; nor can we know _a priori_ but a substance might perhaps exist without any accidents: we only know that accidents cannot exist without some substance, or subject, or power which will sustain them in existence. Can substance be apprehended by the senses, or only by intellect? Strictly speaking, only by intellect: it is neither a “proper object” of any one sense, such as taste, or colour, or sound; nor a “common object” of more than one sense, as extension is with regard to sight and touch: it is, in scholastic language, not a “_sensibile per se_,” not itself an object of sense knowledge, but only “_sensibile per accidens_,” _i.e._ it may be said to be “accidentally” an object of sense because of its conjunction with accidents which are the proper objects of sense: so that when the senses perceive accidents what they are really perceiving is the substance affected by the accidents. But strictly and properly it is by intellect we consciously grasp that which in the reality is the substance: while the external and internal sense faculties make us aware of various qualities, activities, or other accidents external to the “self,” or of various states and conditions of the “self,” the intellect—which is a faculty of the same soul as the sense faculties—makes us simultaneously aware of corporeal substances actually existing outside us, or of the concrete substance of the “ego” or “self,” existing and revealing itself to us in and through its conscious activities, as the substantial, abiding, and unifying subject and principle of these conscious activities. Thus, then, do we attain to the concept of substance in general, to a conviction of the concrete actual existence of that mode of being the essential characteristic of which is “to exist in itself”.