Space and time are known to us as formal conditions of consciousness; whether they are anything more than such conditions is a question which at present we have no means of answering.
The laws of consciousness must be primarily manifested as binding upon the conscious mind. As such, they necessarily accompany every manifestation of consciousness; and in their utmost objective reality they could do no more. But we do not deny the real existence of space and time, though at the present stage of our inquiry we are not able to affirm it. We shall hereafter have occasion to consider whether this question can be answered at all. It is sufficient for the present to say that it cannot be answered by Psychology.
The Matter of intuitive consciousness cannot be specified with the same exactness as the Form; for while in all cognate acts of consciousness the form is one and the same, and therefore admits of a distinct examination apart from the several modes of consciousness into which it enters, the matter is the variable element by which one act’ of consciousness differs from another, and which, therefore, can only be fully analysed by a separate examination of each individual case.
The various phenomena of the matter of consciousness, however, admit of being classified and partially described under certain general heads; and such a classification has accordingly been attempted in the distinctions, which form the substance of most psychological treatises, between the various states, operations, and faculties of the human mind. The Matter of intuitive consciousness, in its widest sense, denotes all that distinguishes one object from another, as given in and by this or that special experience.
Of experience there are two principal sources: 1. Sensation or external intuition, by which we become cognisant of the phenomena connected with our material organisation; and 2. Internal intuition (called by Locke reflection), by which we become cognisant of the several successive states of our own minds. To the former we owe the materials of our knowledge of what takes place without us; from the latter, in like manner, is derived our knowledge of what takes place within us. The subdivisions of these two constitute the several states and operations of the human mind.
***Excerpt from Henry Longueville Mansel, B.d.. Metaphysics or the philosophy of consciousness