  In sum, Habermas's discourse theory aligns different types of validity claim with different types of justificatory discourse. At the logical level, cogent arguments must employ somewhat different sorts of reasons to justify different types of claims. Although some sorts of reasons might enter into each type of discourse (e.g., empirical claims), the set of relevant considerations that are individually necessary and jointly sufficient for making logically strong arguments will differ. Thus, claims about what human beings need are relevant reasons in moral arguments about welfare obligations, but not for supporting the truth claim that quarks exist. At the dialectical level, one must meet different burdens of proof by answering different types of challenges. For example, in defending the ethical authenticity of Tom's pursuit of a career in medicine, one need not show that medicine is a career everyone must follow, but only that such a career makes sense, given Tom's personal background, talents, and desires. One can also examine Tom's career choice from a moral perspective, but in that case one need only show that anyone in his circumstances is morally permitted to pursue medicine. At the rhetorical level, finally, the scope and depth of agreement differs according to the type of claim. Moral rightness claims and empirical truth claims are justified by reasons that should be acceptable to a universal audience, whereas ethical claims are addressed to those who share a particular history and tradition of values. 