 There are three major issues connected with the development of logical frameworks that can adequately represent defeasible reasoning: (i) material adequacy; (ii) formal properties; and (iii) complexity. A non-monotonic formalism is materially adequate to the extent to which it captures examples of defeasible reasoning and to the extent to which it has intuitive properties. The question of formal properties has to do with the degree to which the formalism gives rise to a consequence relation that satisfies desirable theoretic properties such as the above mentioned Reflexivity, Cut, and Cautious Monotony. The third set of issues has to do with computational complexity of the most basic questions concerning the framework. 