15. GROUNDS OF THOSE CHARACTERISTICS.—In considering the grounds or reasons of the various characteristics just enumerated it may be well to reflect that when we speak of the _intrinsic possibility_ of a possible essence we conceive the latter as something complex, which we mentally resolve into its constitutive notes or factors or principles, to see if these are compatible. If they are we pronounce the essence intrinsically possible, if not we pronounce it intrinsically impossible. For our minds, absence of internal incompatibility in the content of our concept of any object is the test of its intrinsic possibility. Whatever fulfils this test we consider capable of existing. But what about the possibility of the notes, or factors, or principles themselves, whereby we define those essences, and by the union of which we conceive those essences to be constituted? How do we know that those abstract principles or factors—no one of which can actually exist alone, since all are abstract—can in certain combinations form _possible_ objects of thought? We can know this only because we have either experienced such objects as actual, or because we infer their possibility from objects actually experienced. And similarly our knowledge of what is impossible is based upon our experience of the actual. Since, moreover, our experience of the actual is finite and fallible, we may err in our judgments as to what essences are, and what are not, intrinsically possible.(91) If now we ask ourselves what intelligible reason can we assign for the characteristics just indicated as belonging to possible essences, we must fix our attention first of all on the fundamental fact that the human intellect always apprehends its object _in an abstract condition_. It contemplates the essence apart from the existence in which the essence is subject to circumstances of time and place and change; it grasps the essence in a static condition as simply identical with itself and distinct from all else; it sees the essence as indifferent to existence at any place or time; reflecting then on the actualization of this essence in the existing order of things, it apprehends the essence as capable of indefinite actualizations (except in cases where it sees some reason to the contrary), _i.e._ it _universalizes_ the essence; comparing it with its constituent notes or elements, and with those of other essences, it sees and affirms certain relations (of identity or diversity, compatibility or incompatibility, between those notes or elements) as holding good _necessarily_ and _immutably_, and independently of the actual embodiment of those notes or elements in any object existing at any particular place or time. All these features of the relations between the constituents of abstract, possible essences, seem so far to be adequately accounted for by the fact that the intellect apprehends those essences _in the abstract_: the data in which it apprehends them being given to it