Fourteen of the American philosopher's most influential essays appear here, offering profound reflections on many different aspects of knowledge, reality, and epistemology. These papers on experimental logic are rooted in the implication that possession of knowledge implies a judgment, resulting from an inquiry or investigation. The presence of this 'inquiry stage' suggests an intermediate and mediating phase between the external world and knowledge, an area conditioned by other factors. Expanding upon this basis, these essays consider the relationship of thought and its subject matter; the antecedents and stimuli of thought, data, and meanings; the objects of thought; control of ideas by facts; and similar topics. Unabridged republication of the classic 1916 edition.