Current practice in logic increasingly accords recognition to abductive, presumptive or plausible arguments, in addition to deductive and inductive arguments. But there is uncertainty about what these terms exactly mean, what the differences between them are (if any), and how they relate. By examining some analyses ofthese terms and some of the history of the subject (including the views of Peirce and Cameades), this paper sets out considerations leading to a set of definitions, discusses the relationship of these three forms (...) of argument to argumentation schemes and sets out a new argumentation scheme for abductive argument. (shrink)

Consistency is often pictured as an indispensable requisite for rationality. The paper argues that this is overly rigoristic. Inconsistency can be treated as a matter of isolable singularities rather than an all-destructive disaster. The paper, supports and illustrates a perspective on which consistency can be seen as a desideratum rather than a totaly non-negotiable demand. The argumentation of the paper casts consistency in the role of a cognitive ideal rather than a sine qua non condition of rational process.