can return to nothing,” is everywhere assumed and has been frequently advanced, but never yet proved, for, indeed, it is impossible to prove it dogmatically.  Here the only possible proof for it, the critical proof, is given:  the principle of permanence is a necessary condition of experience.  The same argument establishes the principle of sufficient reason, and the principle of the community of substances, together with the unity of the world to be inferred from this.  The three Analogies together assert:  “All phenomena exist in one nature and must so exist, because without such a unity a priori no unity of experience, and therefore no determination of objects in experience, would be possible.”—­In connection with the Postulates the same transcendental proof is given for a series of other laws of nature a priori, viz., that in the course of the changes in the world—­for the causal principle holds only for effects in nature, not for the existence of things as substances—­there can be neither blind chance nor a blind necessity (but only a conditional, hence an intelligible, necessity); and, further, that in the series of phenomena, there can be neither leap, nor gap, nor break, and hence no void—­in mundo non datur casus, non datur fatum, non datur saltus, non datur hiatus.

While the dynamical principles have to do with the relation of phenomena, whether it be to one another (Analogies), or to our faculty of cognition (Postulates), the mathematical relate to the quantity of intuitions and sensations, and furnish the basis for the application of mathematics to natural science.[1] An extensive quantity is one in which the representation of the parts makes the representation of the whole possible, and so precedes it.  I cannot represent a line without drawing it in thought, i.e., without producing all parts of it one after the other, starting from a point.  All phenomena are intuited as aggregates or as collections of previously given parts.  That which geometry asserts of pure intuition (i.e., the infinite divisibility of lines) holds also of empirical intuition.  An intensive quantity is one which is apprehended only as unity, and in which plurality can be represented only by approximation to negation = 0.  Every sensation, consequently every reality in phenomena, has a degree, which, however small it may be, is never the smallest, but can always be still more diminished; and between reality and negation there exists a continuous connection of possible smaller intermediate sensations, or an infinite series of ever decreasing degrees.  The property of quantities, according to which no part in them is the smallest possible part, and no part is simple, is termed their continuity.  All phenomena are continuous quantities, i.e., all their parts are in turn (further divisible) quantities.  Hence it follows, first, that a proof for an empty space or empty time can never be drawn from experience, and secondly, that all change is also continuous.  “It is remarkable,” so Kant ends his proof of the Anticipation, “that of quantities in general we can know one quality only a priori, namely, their continuity, while with regard to quality (the real of phenomena) nothing is known to us a priori but their intensive quantity, that is, that they must have a degree.  Everything else is left to experience.”