Is there really a theory of chance? I believe that a direct treatment of the subject is impossible. The problem of chance can be only approximately explained when all conceivable chance-happenings of a given discipline are brought together and their number reduced by careful search for definite laws. Besides, the problem demands the knowledge of an extremely rich casuistry, by means of which, on the one hand, to bring together the manifoldness of chance events, and on the other to discover order. Enough has been written about chance, but a systematic treatment of it must be entirely theoretical. So Windelband’s[150] excellent and well-ordered book deals with relations (chance and cause, chance and law, chance and purpose, chance and concept) the greatest value of which is to indicate critically the various definitions of the concept of chance. Even though there is no definition which presents the concept of chance in a completely satisfactory manner, the making of such definitions is still of value because one side of chance is explained and the other is thereby seen more closely. Let us consider a few of these and other definitions. Aristotle says that the accidental occurs, παρἁ φὑσν, according to nature. Epicurus, who sees the creation of the world as a pure accident, holds it to occur τἁ μἑν ἁπὁ τὑχης, τἁ δἑ παρ’ἡμὡν. Spinoza believes nothing to be contingent save only according to the limitations of knowledge; Kant says that conditioned existence as such, is called accidental; the unconditioned, necessary. Humboldt: “Man sees those things as accident which he can not explain genetically.” Schiel: “Whatever may not be reduced back to law is called accidental.” Quetelet: “The word chance serves officiously to hide our ignorance.” Buckle derives the idea of chance from the life of nomadic tribes, which contains nothing firm and regulated. According to Trendelenburg chance is that which could not be otherwise. Rosenkranz says: Chance is a reality which has only the value of possibility, while Fischer calls chance the individualized fact, and Lotze identifies it with everything that is not valid as a natural purpose. For Windelband “chance consists, according to usage, in the merely factual but not necessary transition from a possibility to an actuality. Chance is the negation of necessity. It is a contradiction to say: ‘This happened by accident,’ for the word ‘by’ expressed a cause.” A. Höfler[151] says most intelligently, that the contradiction of the idea of chance by the causal law may be easily solved by indicating the especial relativity of the concept. (Accidental with regard to one, but otherwise appearing as a possible causal series).