In this paper, I present the fundamental ideas of a new theory of justification strength. This theory is based on the epistemological approach to argumentation. Even the thesis of a valid justification can be false for various reasons. The theory outlined here identifies such possible errors. Justification strength is equated with the degree to which such possible errors are excluded. The natural expression of this kind of justification strength is the (rational) degree of certainty of the belief in the thesis.

In this paper an empirical theory about the nature of intention is sketched. After stressing the necessity of reckoning with intentions in philosophy of action a strategy for deciding empirically between competing theories of intention is exposed and applied for criticizing various philosophical theories of intention, among others that of Bratman. The hypothesis that intentions are optimality beliefs is defended on the basis of empirical decision theory. Present empirical decision theory however does not provide an empirically satisfying elaboration of the (...) desirability concepts used in these optimality beliefs. Based on process theories of deliberation two hypotheses for filling this gap are developed. (shrink)

Tu quoque arguments regard inconsistencies in some speaker‘s performance. Most tu quoque arguments depend on actual inconsistencies. However, there are forms of tu quoque arguments that key, instead, on the conflicts a speaker would have, were some crucial contingent fact different. These, we call subjunctive tu quoque arguments. Finally, there are cases wherein the counterfactual inconsistencies of a speaker are relevant to the issue.

The paper develops a classificatory system of basic argument types on the basis of the epis-temological approach to argumentation. This approach has provided strict rules for several kinds of argu-ments. These kinds may be brought into a system of basic irreducible types, which rely on different parts of epistemology: deductive logic, probability theory, utility theory. The system reduces a huge mass of differ-ent argument schemes to basic types and gives them an epistemological foundation.