It is now possible to direct attention to two characteristics of perception and knowledge with which Kant's treatment of space and time conflicts, and the recognition of which reveals his procedure in its true light.
It has been already urged that both knowledge and perception--which, though not identical with knowledge, is presupposed by it--are essentially of _reality_. Now, in the _first_ place, it is thereby implied that the relation between the mind and reality in knowledge or in perception is essentially direct, i. e. that there is no _tertium quid_ in the form of an 'idea' or a 'representation' between us as perceiving or knowing and what we perceive or know. In other words, it is implied that Locke's view is wrong in principle, and, in fact, the contrary of the truth. In the _second_ place, it is implied that while the whole fact of perception includes the reality perceived and the whole fact of knowledge includes the reality known, since both perception and knowledge are 'of', and therefore inseparable from a reality, yet the reality perceived or known is essentially distinct from, and cannot be stated in terms of, the perception or the knowledge. Just as neither perception nor knowledge can be stated in terms of the reality perceived or known from which they are distinguished, so the reality perceived or known cannot be stated in terms of the perception or the knowledge. In other words, the terms 'perception' and 'knowledge' ought to stand for the activities of perceiving and knowing respectively, and not for the reality perceived or known. Similarly, the terms 'idea' and 'representation'--the latter of which has been used as a synonym for Kant's _Vorstellung_--ought to stand not for something thought of or represented, but for the act of thinking or representing.
Further, this second implication throws light on the proper meaning of the terms 'form of perception' and 'form of knowledge or of thought'. For, in accordance with this implication, a 'form of perception' and a 'form of knowledge' ought to refer to the nature of our acts of perceiving and knowing or thinking respectively, and not to the nature of the realities perceived or known. Consequently, Kant was right in making the primary antithesis involved in the term 'form of perception' that between a way in which we perceive and a way in which things are, or, in other words, between a characteristic of our perceiving nature and a characteristic of the reality perceived. Moreover, Kant was also right in making this distinction a real antithesis and not a mere distinction within one and the same thing regarded from two points of view. That which is a form of perception cannot also be a form of the reality and vice versa. Thus we may illustrate a perceived form of perception by pointing out that our apprehension of the physical world (1) is a temporal process, and (2) is conditioned by perspective. Both the succession and the conditions of perspective belong to the act of perception, and do not form part of the nature of the world perceived. And it is significant that in our ordinary consciousness it never occurs to us to attribute either the perspective or the time to the reality perceived. Even if it be difficult in certain cases, as in that of colour, to decide whether something belongs to our act of perception or not, we never suppose that it can be _both_ a form of perception _and_ a characteristic of the reality perceived. We think that if it be the one, it cannot be the other.