"A priori" in the scientific vs. philosophic case?

[progressiveman1]

I myself didn't understand why the ASD distinction was invalid until I read P's paper, and I've been professionally acquainted with the distinction for a number of decades;

What problems did it cause you during that time, before reading Peikoff's essay?

symbol-manipulative deductive logic.

What's that?

[DavidOdden]

What problems did it cause you during that time, before reading Peikoff's essay?

Primarily that there is no way to formally distinguish "analytic" and "synthetic" sentences, and also that most supposedly analytic sentences are analytic only if you assume a specific reading of a word (example: the ostensively analytic sentence "All batchelors are male" is analytic only when you use the word with the intended reading "unmarried male". Under the "baccalaureate" readng, it's plainly false, and under the "young knight in service of another knight" reading, it's only synthetically true because of a cultural thing about knights in feudal times).

What's that?

For example, logic can be done by systems of axioms like "(p>(q>r)) > ((p>q)>(p>r))" and symbol substitution. The main characteristic is that an arbitrary collection of symbols can be introduced (involving variables and connectives) and there are rules telling you when you can introduce new collections of symbols from the previous set of symbols. The Katz-Fodor theory attempted to do this, though it was, shall I be charitable? a "promising failure".