form of our perception by fixing one's eyes upon the powerlessness of time as opposed to natural forces. If, for example, a rotatory motion is imparted to a planet by some external cause, if no new cause enters to stop it, this motion will endure for ever. This could not be so if time were something in itself and had an objective, real existence: for then it would necessarily also produce some effect. Thus we see here, on the one hand, the forces of nature, which manifest themselves in that rotation, and, if it is once begun, carry it on for ever without becoming weary or dying out, prove themselves to be eternal or timeless, and consequently absolutely real and existing in themselves; and, on the other hand, time as something which consists only in the manner in which we apprehend that phenomenon, since it exerts no power and no influence upon the phenomenon itself; for what does not act is not.
We have a natural inclination whenever it is possible to explain every natural phenomenon mechanically; doubt less because mechanics calls in the assistance of the fewest original, and hence inexplicable, forces, and, on the other hand, contains much that can be known a priori, and therefore depends upon the forms of our own intellect, which as such carries with it the highest degree of comprehensibility and clearness. However, in the "Metaphysical First Principles of Natural Science" Kant has referred mechanical activity itself to a dynamical activity. On the other hand, the application of mechanical explanatory hypotheses, beyond what is demonstrably mechanical, to which, for example, Acoustics also belongs, is entirely unjustified, and I will never believe that even the simplest chemical combination or the dfference of the three states of aggregation will ever admit of mechanical explanation, much less the properties of light, of heat, and electricity. These will always admit only of a dynamical explanation, i.e., one which explains the phenomenon from original forces which are entirely different from those of impact, pressure,
