The concepts of categorical diagnosis and conjectural diagnosis are introduced. It is argued that in diagnostic reasoning conjectural diagnosis plays a more important role than categorical diagnosis. Attention is called to the inevitable vagueness of clinical language and to the suitability of epistemic logic and fuzzy logic for diagnostic reasoning.

After giving a short summary of the traditional theory of the syllogism, it is shown how the square of opposition reappears in the much more powerful concept logic of Leibniz. Within Leibniz’s algebra of concepts, the categorical forms are formalized straightforwardly by means of the relation of concept-containment plus the operator of concept-negation as ‘S contains P’ and ‘S contains Not-P’, ‘S doesn’t contain P’ and ‘S doesn’t contain Not-P’, respectively. Next we consider Leibniz’s version of the so-called Quantification of (...) the Predicate which consists in the introduction of four additional forms ‘Every S is every P’, ‘Some S is every P’, ‘Every S isn’t some P’, and ‘Some S isn’t some P’. Given the logical interpretation suggested by Leibniz, these unorthodox propositions also form a Square of Opposition which, when added to the traditional Square, yields a “Cube of Opposition”. Finally it is shown that besides the categorical forms, also the non-categorical forms can be formalized within an extension of Leibniz’s logic where “indefinite concepts” X, Y, Z\ function as quantifiers and where individual concepts are introduced as maximally consistent concepts. (shrink)

Epistemic minimalism affirms that mere true belief is sufficient for propositional knowledge. I construct a taxonomy of some specific forms of minimalism and locate within that taxonomy the distinct positions of various advocates of minimalism, including Alvin Goldman, Jaakko Hintikka, Crispin Sartwell, Wolfgang Lenzen, Franz von Kutschera, and others. I weigh generic minimalism against William Lycan’s objection that minimalism is incompatible with plausible principles about relations between knowledge, belief, and confidence. I argue that Lycan’s objection fails for equivocation but that (...) some specific forms of minimalism are better able than others to articulate that defense. (shrink)

Ivan Boh affirms and Robert Pasnau denies that William Heytesbury holds merely true belief to be sufficient for knowledge in the broad sense. I argue that Boh is correct and Pasnau is mistaken, and that there is a long-running orthodox medieval tradition agreeing with Heytesbury about the conditions for knowledge. I offer a hypothesis about the origins, continuance and demise of that medieval tradition, and some remarks about the tradition's significance.