The topic of this study is to what extent standards of rational inquiry can be rationally criticized and revised. It is argued that it is rational to treat all such standards as open to criticism and revision. Arguments to the effect that we are fallible with regard to all standards of rational inquiry are presented. Standards cannot be ultimately justified and with certainty established either as adequate or as inescapable presuppositions. Apel's attempt to give ultimate justifications of certain moral and logical rules is examined and criticized. Special attention is given to our fallibility with regard to logical inference rules. The idea that certain logical rules cannot be put into question because any critical argument presupposes them is criticized. It has been claimed that there must be some basic standards which are such that they cannot be rationally evaluated and hence are rationally unrevisable. This is called "the unrevisability thesis". Related to this thesis is the normative policy according to which rationality requires that some standards be treated as unrevisable, the unrevisability policy. Two arguments that have been used to defend the unrevisability thesis and policy are examined and criticized. The conclusion is that we are not forced to accept either the thesis or the policy. The negation of the unrevisability policy is the revisability policy, according to which it is rational to treat all standards as open to rational criticism and revision. Objections that have been directed against the revisability policy are discussed and criticized. According to the objections, the revisability policy leads to rationality relativism. These objections are refuted, and it is argued that it is, on the contrary, rational to adopt the revisability policy and treat all standards of rational inquiry as criticizable and revisable. It is proposed that the rational change of standards should be viewed as a bootstrap process. General features of a bootstrap view of rational change of standards are presented, and it is argued that it is impossible to formulate a real theory of bootstrapping. Two models of standard change are presented and discussed: Laudan's reticulated model of scientific rationality and Briskman's bootstrap theory. It is claimed that in spite of defects and limitations, these models contribute to a richer understanding of bootstrapping. The fallibility and revisability of standards of rational inquiry have consequences for how the normativity of rationality should be understood. The book ends with an account of how the rationality of cognitive actions is related to the idea of the adequacy of standards. A distinction between absolute and standard-relative rationality is made, and it is argued that what an inquiring agent rationally ought to do coincides with what it is standard-relatively rational for him to do. It is shown that this view of rationality of inquiry is nevertheless inconsistent with rationality relativism, and that it is compatible with an objectivistic view of rationality. / digitalisering@umu