The first class of objects possible to our representative faculty, is that of _intuitive, complete, empirical_ representations. They are _intuitive_ as opposed to mere thoughts, _i.e._ abstract conceptions; they are _complete_, inasmuch as, according to Kant's distinction, they not only contain the formal, but also the material part of phenomena; and they are _empirical_, partly as proceeding, not from a mere connection of thoughts, but from an excitation of feeling in our sensitive organism, as their origin, to which they constantly refer for evidence as to their reality: partly also because they are linked together, according to the united laws of Space, Time and Causality, in that complex without beginning or end which forms our _Empirical Reality_. As, nevertheless, according to the result of Kant's teaching, this _Empirical Reality_ does not annul their _Transcendental Ideality_, we shall consider them here, where we have only to do with the formal elements of knowledge, merely as representations. § 18. _Outline of a Transcendental Analysis of Empirical Reality._ The forms of these representations are those of the inner and outer sense; namely, _Time_ and _Space_. But these are only _perceptible_ when _filled_. Their _perceptibility_ is _Matter_, to which I shall return further on, and again in § 21. _If Time were the only form_ of these representations, there could be no _coexistence_, therefore nothing _permanent_ and no _duration_. For _Time_ is only perceived when filled, and its course is only perceived by the _changes_ which take place in that which fills it. The _permanence_ of an object is therefore only recognized by contrast with the _changes_ going on in other objects _coexistent_ with it. But the representation of _coexistence_ is impossible in Time alone; it depends, for its completion, upon the representation of _Space_; because, in mere Time, all things _follow one another_, and in mere Space all things are _side by side_; it is accordingly only by the combination of Time and Space that the representation of coexistence arises. _On the other hand, were Space the sole form_ of this class of representations, there would be no _change_; for change or alteration is _succession_ of states, and _succession_ is only possible in _Time_. We may therefore define Time as the possibility of opposite states in one and the same thing.