He was a philosopher, whose work in the late 1800s was a precursor to computer science. Practical applications have been found in modern research.

http://en.wikipedia.org/wiki/Charles_Sanders_Peirce

"Peirce considered himself, first and foremost, a logician. He made major contributions to logic, but logic for him encompassed much of that which is now called epistemology and philosophy of science. He saw logic as the formal branch of semiotics, of which he is a founder. As early as 1886 he saw that logical operations could be carried out by electrical switching circuits; the same idea was used decades later to produce digital computers."

http://plato.stanford.edu/entries/peirce/#con

"Currently, considerable interest is being taken in Peirce's ideas by researchers wholly outside the arena of academic philosophy. The interest comes from industry, business, technology, intelligence organizations, and the military; and it has resulted in the existence of a substantial number of agencies, institutes, businesses, and laboratories in which ongoing research into and development of Peircean concepts are being vigorously undertaken."