devotes a chapter to his "induction principle". He describes it as coming in two parts: firstly, as a repeated collection of evidence (with no failures of association known) and therefore increasing probability that whenever A happens B follows; secondly, in a fresh instance when indeed A happens, B will indeed follow: i.e. "a sufficient number of cases of association will make the probability of a fresh association nearly a certainty, and will make it approach certainty without limit." He then collects all the cases (instances) of the induction principle (e.g. case 1: A1 = "the rising sun", B1 = "the eastern sky"; case 2: A2 = "the setting sun", B2 = "the western sky"; case 3: etc.) into a "general" law of induction which he expresses as follows: "(a) The greater the number of cases in which a thing of the sort A has been found associated with a thing of the sort B, the more probable it is (if cases of failure of association are known) that A is always associated with B; "(b) Under the same circumstances, a sufficient number of cases of the association of A with B will make it nearly certain that A is always associated with B, and will make this general law approach certainty without limit." He makes an argument that this induction principle can neither be disproved or proved by experience, the failure of disproof occurring because the law deals with probability of success rather than certainty; the failure of proof occurring because of unexamined cases that are yet to be experienced, i.e. they will occur (or not) in the future. "Thus we must either accept the inductive principle on the ground of its intrinsic evidence, or forgo all justification of our expectations about the future". In his next chapter ("On Our Knowledge of General Principles") Russell offers other principles that have this similar property: "which cannot be proved or disproved by experience, but are used in arguments which start from what is experienced." He asserts that these "have even greater evidence than the principle of induction ... the knowledge of them has the same degree of certainty as the knowledge of the existence of sense-data. They constitute the means of drawing inferences from what is given in sensation". Inference principle: Russell then offers an example that he calls a "logical" principle. Twice previously he has asserted this principle, first as the