Page:Kant's Prolegomena etc (1883).djvu/356

 transformation of illusion into truth, but of phenomenon into experience. For with illusion the understanding is always engaged with its own judgment determining an object—although it is in danger of mistaking the subjective for objective—but in the phenomenon no judgment of the understanding is to be met with; and this is necessary to be remembered, not only here, but in the whole of philosophy, because, otherwise, when we are concerned with phenomena, and this expression is taken as identical in signification with that of illusion, misunderstanding will always arise.

The rectilinear motion of a matter is, in respect of an empirical space, as distinguished from the opposite motion of the space, a merely possible predicate. The same [thing] conceived in no relation to a matter outside it, that is, as absolute motion, is impossible.

Demonstration. Whether [in the case of] a body moved in relative space, this latter be described as resting, or conversely, as moved with equal velocity in an opposite direction, and the former as resting, there is no statement as to what belongs to the object, but only to its relation to the subject, in other words, to the phenomenon and not to experience. For if the spectator place himself in the samo space as resting, he terms the body moved; but if he place himself (at least in thought) in another space enclosing this, in respect of which the body is, in the same way, resting, then the relative space is termed "moved." In experience, therefore (a cognition, determining validly the object for all phenomena), there is no difference whatever between the motion of the body in relative space, or the rest of the body in absolute, and the equal and opposite motion of the relative, space. Now the presentation of an object by one of its two predicates—which, in respect of the object, are equivalent, and only as regards the subject and its mode of presentation distinguished from one another—is not its determination according to a disjunctive, but merely an alternative judgment according to choice (of which