Preyer seems to make a mistake similar to that of those who efface sensation and motion, when, in an essay on the hypothesis of the origin of life, in the "Deutsche Rundschau," Vol. I, 7, he even effaces the difference between life and sensation, and simply identifies life and motion. "Self-motion, called life, and inorganic movement of bodies by agencies outside of themselves, are but quantitatively, intensively, or gradually different forms of motion; not in their innermost being different.... Our will changes many kinds of motion into heat, makes {137} cold metal to be red-hot simply by hammering.... Likewise inversely, as the law of the conservation of force must require, a part of the eternal heat of the metal can be now and forever transposed into the living motion of our soul." This whole manner of investigation and proof is one of those numerous unconscious logical fallacies which, introduced by Hegel, have gradually attained a certain title by possession. From the observation of a process, they abstract a characteristic, as general as possible,--as, for instance, from the observation of life the characteristic of motion; then they find that the process has the characteristic in common with still other processes--as, for instance, the self-motion of the living has the general characteristic of motion in common with the objective motion of the lifeless; and then they persuade themselves that the process which they try to explain is really explained by having found a quality of this process as comprehensive as possible. And in order to hide the falsity of the conclusion, they also give to the general idea, which they have found to be a characteristic of that process, the same name which the special process has,--as, for instance, they call motion life, no matter whether it is a motion of itself or a being moved, no matter whether it is performed from within or in consequence of an impulse from without; and then they say: "Behold, life is explained; life is nothing but motion." But it can be readily seen that life is also motion, and has therefore this characteristic in common with everything which is moved; but that the specific of that motion called life--namely, self-motion in consequence of an impulse renewing itself from within, and, as Fechner shows, {138} self-motion in a rotatory direction of the molecules, precisely the same thing which in distinction from other motions we call life,--is not explained, but simply ignored.