Now as, notwithstanding this union through the Understanding of the forms of the inner and outer sense in representing Matter and with it a permanent outer world, all _immediate_ knowledge is nevertheless acquired by the Subject through the _inner_ sense alone--the outer sense being again Object for the inner, which in its turn perceives the perceptions of the outer--and as therefore, with respect to the _immediate presence_ of representations in its consciousness, the Subject remains under the rule of _Time_ alone, as the form of the _inner sense_:[56] it follows, that only one representation can be present to it (the Subject) at the same time, although that one may be very complicated. When we speak of representations as _immediately present_, we mean, that they are not only known in the union of Time and Space effected by the Understanding--an intuitive faculty, as we shall soon see--through which the collective representation of empirical reality arises, but that they are known in mere Time alone, as representations of the inner sense, and just at the neutral point at which its two currents separate, called the _present_. The necessary condition mentioned in the preceding paragraph for the immediate presence of a representation of this class, is its causal action upon our senses and consequently upon our organism, which itself belongs to this class of objects, and is therefore subject to the causal law which predominates in it and which we are now about to examine. Now as therefore, on the one hand, according to the laws of the inner and outer world, the Subject cannot stop short at that one representation; but as, on the other hand, there is no coexistence in Time alone: that single representation must always vanish and be superseded by others, in virtue of a law which we cannot determine _à priori_, but which depends upon circumstances soon to be mentioned. It is moreover a well-known fact, that the imagination and dreams reproduce the immediate presence of representations; the investigation of that fact, however, belongs to empirical Psychology. Now as, notwithstanding the transitory, isolated nature of our representations with respect to their immediate presence in our consciousness, the Subject nevertheless retains the representation of an all-comprehensive complex of reality, as described above, by means of the function of the Understanding; representations have, on the strength of this antithesis, been viewed, as something quite different when considered as belonging to that complex than when considered with reference to their immediate presence in our consciousness. From the former point of view they were called _real things_; from the latter only, representations κατ' ἐξοχήν. This view of the matter, which is the ordinary one, is known under the name of _Realism_. On the appearance of modern philosophy, _Idealism_ opposed itself to this _Realism_ and has since been steadily gaining ground.