## Abstract

This paper gives an explication of our intuitive notion of strength of justification in a controversial debate. It defines a thesis’ degree of justification within the theory of dialectical structures as the ratio of coherently adoptable positions according to which that thesis is true over all coherently adoptable positions. Broadening this definition, the notion of conditional degree of justification, i.e. degree of partial entailment, is introduced. Thus defined degrees of justification correspond to our pre-theoretic intuitions in the sense that supporting and defending a thesis *t* increases, whereas attacking it decreases, *t*’s degree of justification. Moreover, it is shown that (conditional) degrees of justification are (conditional) probabilities. Eventually, the paper explains that it is rational to believe theses with a high degree of justification inasmuch as this strengthens the robustness of one’s position.

## Keywords

Partial Position Rational Belief Argumentation Framework Inferential Relation Dialectical Structure## Notes

### Acknowledgments

The author would like to thank the tau-Klub at Freie Universitaet Berlin and members of the Department of Computer Science at the University of Liverpool for discussing an earlier version of this article. Moreover, he is particularly grateful to two anonymous reviewers of Erkenntnis for their astute and helpful comments.

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