Form, variation and deducibility in the logic of Bolzano (Q2714830)

The author claims that a basic notion in the logic outlined in Bolzano's \textit{Wissenschaftslehre} (1837), is that of variation, which is effected by substitutional means on modern logic (and also, one might add, by Russell in a period of enthusiasm in the mid 1900s). He describes how variations were effected relative to the form of a proposition, and how Bolzano handled related notions such as the analyticity of proposition, and of its deducibility from another one (usually with in the framework of syllogisms). However, the author notes that Bolzano made no distinction between logical and meta-logical notions; and he discusses other ways in which Bolzano's notion of logical consequence is (dis-)similar to that of Tarski.