THE CONCEPT of human will, the correct interpretation of which is essential to the subject of this treatise, implies a twofold meaning. Since all mental action involves thinking. I distinguish between the will which includes the thinking and the thinking which encompasses the will. Each represents an inherent whole which unites in itself a multiplicity of feelings, instincts, and desires. This unity should in the first case be understood as a real or natural one; in the second case as a conceptual or artificial one. The will of the human being in the first form I call natural will (Wesenwille); in the second form, rational will (Kürwille).