Robert Mayer, the talented discoverer of the equivalent of heat, has proven that the force of gravitation, of electricity, of steam, of heat, etc., represents different modes of expression of the same force, of the force of nature in general. But no, not quite so! He has ascertained the numerical relation by which the transformations of one force into another is accomplished. Thus a logical understanding sees that the various forces and force in general are distinguished in detail but identical in general. Darwin in his "Origin of Species" has accomplished a similar demonstration. But neither Mayer nor Darwin have given that general expression to world unity which is required by the art of logic. In order to become an adept at this art, you must rise to the understanding that all forces are various modes of expression of the one force, all animals and species transformations of animaldom, that on the moon a part is smaller than the whole, the same as on earth, that there as well as here fire burns, and that as surely as you have no doubt of your being, just as surely is there only one being, the infinite, divine universe which has no other gods beside it, but contains all forces, materials, and transformations. This is an innate science which is the cause of all other science, an innate science which, indeed, must first be awakened in you by "memory." Hence our proletarian logic instructs you not to rack your brain by mere introspection, as the ancient philosophers used to do, not to call the senses impostors nor to search for truth without eyes, nose, and ears, nor on the other hand to start out with the idea of certain natural scientists who try to see, hear, and smell understanding without the help of the intellect. The mistake committed in making a wrong use of the intellect is a "sin against the holy ghost." The Socratic-Platonic doctrine of memory is one extreme side of this sin; the other extreme side is represented by that modern science which tries to find truth by mere external means and rejects everything as untrue which is not ponderable or tangible. As this letter is more intimately connected with the following one than is ordinarily the case, I take the liberty to unite them under the same number and mark them with the letters A and B. (B)