SummaryScientists regard their inductive hypotheses as confirmed when consistence exists between two or more results obtained by differing methods. Three hierarchical levels of confirmation are applied. Certainty is obtained by the deductive element of the third level. The question of uniformity o i nature is less decisive than the question whether or not the complexity of the processes observed or the limited scope of our senses and instruments permits to see through the causal connections involved.

The model function for induction of Goodmans's composite predicate "Grue" was examined by analysis. Two subpredicates were found, each containing two further predicates which are mutually exclusive (green and blue, observed before and after t). The rules for the inductive processing of composite predicates were studied with the more familiar predicate "blellow" (blue and yellow) for violets and primroses. The following rules for induction were violated by processing "grue": From two subpredicates only one (blue after t) appears in the conclusion. (...) As a statement about a future and unobserved condition this subpredicate, however, is not projectible for induction whereas the only suitable predicate (green before t) does not show up in the conclusion. In a disjunction "a v b" where "a" is true and "b" false the disjunction is true. When, however, the only true component is dropped, what remains is necessarily false. An analogous mistake may be observed in the processing of "grue", where the only true component (green) was dropped in the conclusion. - As a potent criterion for correct inductions a check of the necessity of the conclusions is recommended. (shrink)

The probabilistic corroboration of two or more hypotheses or series of observations may be performed additively or multiplicatively . For additive corroboration (e.g. by Laplace's rule of succession), stochastic independence is needed. Inferences, based on overwhelming numbers of observations without unexplained counterinstances permit hyperinduction , whereby extremely high probabilities, bordering on certainty for all practical purposes may be achieved. For multiplicative corroboration, the error probabilities (1 - Pr) of two (or more) hypotheses are multiplied. The probabilities, obtained by reconverting the (...) product, are valid for both of the hypotheses and indicate the gain by corroboration.. This method is mathematically correct, no probabilities > 1 can result (as in some conventional methods) and high probabilities with fewer observations may be obtained, however, semantical independence is a prerequisite. The combined method consists of (1) the additive computation of the error probabilities (1 - Pr) of two or more single hypotheses, whereby arbitrariness is avoided or at least reduced and (2) the multiplicative procedure . The high reliability of Empirical Counterfactual Statements is explained by the possibility of multiplicative corroboration of "all-no" statements due to their strict semantical independence. (shrink)