Bernard Bolzano

(1781-1848)

"[The Wissenschaftslehre] in its treatment of the logical 'theory of elements' far surpasses anything that world-literature has to offer in the way of a systematic sketch of logic. Bolzano did not, of course, expressly discuss or support any independent demarcation of pure logic in our sense, but he provided one de facto in the first two volumes of his work, in his discussions of what underlay a Wissenschaftslhere or theory of science in the sense of his conception; he did so with such purity and scientific strictness, and with such a rich store of original, scientifically confirmed and fruitful thoughts, that we must count him as one of the greatest logicians of all time.

He must be placed historically in fairly close proximity to Leibniz, with whom he shares important thoughts and fundamental conceptions, and to whom he is also philosophically akin in other respects."

Edmund Husserl - Logical Investigations - vol. I - Prolegomena to a pure logic § 61 (Appendix) (1900).