We have a natural inclination whenever it is possible to explain every natural phenomenon _mechanically_; doubtless 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 difference 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, weight, &c., and are therefore of a higher kind, _i.e._, are more distinct objectifications of that will which obtains visible form in all things. I am of opinion that light is neither an emanation nor a vibration; both views are akin to that which explains transparency from pores and the evident falseness of which is proved by the fact that light is subject to no mechanical laws. In order to obtain direct conviction of this one only requires to watch the effects of a storm of wind, which bends, upsets, and scatters everything, but during which a ray of light shooting down from a break in the clouds is entirely undisturbed and steadier than a rock, so that with great directness it imparts to us the knowledge that it belongs to another order of things than the mechanical: it stands there unmoved like a ghost. Those constructions of light from molecules and atoms which have originated with the French are indeed a revolting absurdity. An article by Ampère, who is otherwise so acute, upon light and heat, which is to be found in the April number of the “_Annales de chimie et physique_,” of 1835, may be considered as a flagrant expression of this, and indeed of the whole of atomism in general. There the solid, the fluid, and the elastic consist of the same atoms, and all differences arise solely from their aggregation; nay, it is said that space indeed is infinitely divisible, but not matter; because, if the division has been carried as far as the atoms, the further division must fall in the spaces between the atoms! Light and heat, then, are here vibrations of the atoms; and sound, on the other hand, is a vibration of the molecules composed of the atoms. In truth, however, these atoms are a fixed idea of the French savants, and therefore they just speak of them as if they had seen them.