Scientist, mathematician, thinker, the father of pragmatism, the inspiration for William James and John Dewey, Charles Peirce has remained until recently a philosopher’s philosopher. Peirce trod a fine line between the extremes of nominalism and realism, tough-minded pragmatism and metaphysical speculation. As Peter Skagestad makes clear, Peirce’s system of thought was fragmented, incomplete, and sometimes inconsistent. But one overriding concern gives unity to the whole: the road of inquiry must never be blocked.