In adopting the term presentation or intuition, to express the consciousness of any individual affection of the mind, a writer may be liable to the charge of innovation, in what was, at least in the last generation, the established language of English philosophy. But in this case necessity has no law.
We need a term which shall indifferently express the presence of an individual sight or sound in the eye or ear, and of an individual emotion or volition in the mind; and if none such exists in current use, there is no resource but to coin one. It may be added, that if such a term had been in use in the days of Locke, his writings need not have been liable to the perpetual misunderstanding which arises from his ambiguous use of the term reflection. The same apology must serve for the occasional introduction of other philosophical terms, which, though gradually coming into use, are hardly as yet in general circulation.
Preservative consciousness, thus distinguished, appears, like all consciousness, in the form of a relation between the subject or person conscious, and the object, or that of which he is conscious. These two terms are correlative to each other, and imply each other. The subject is a subject to the object, and the object is an object to the subject. The subject can only be conscious by knowing itself to be affected in a particular manner by an object; the object can only be known as affecting the subject in a particular manner.
Thus the two are given in relation as mutually determining and determined by each other. We are affected in various manners by various objects presented to us. But these objects again exist for us as objects, only in so far as they are discerned by our faculties of consciousness. The subject and the object are thus only cognisable as existing in and affected by their mutual relation. We cannot be conscious of a pure ego, or subject affected in no particular manner; nor yet of a pure non ego, or object out of relation to our own cognitive powers.
Hence arises a distinction between phenomena, or things in consciousness, and things in themselves, or things out of consciousness. We know the object only as it stands in relation to our faculties, and is modified by them. We are not sure that, if our faculties were altered, the same things would appear to us in the same form as they do now: we are not sure that they do appear in the same form to all existing intelligent beings; for we know not how far the faculties of other beings resemble our own. But, on the other hand, we have no right to dogmatise on the negative side, and to assume, with equal absence of ground, that things are not in themselves as they appear to us.
***Excerpt from Henry Longueville Mansel, B.d.. Metaphysics or the philosophy of consciousness