Percy has been studied under several headings: Catholic, Southerner, Existentialist. Two such aspects, however, have been neglected: the strong influence of Charles Sanders Peirce, plus Percy's deep competence in laboratory science. His typescript essay, "Peirce and Modern Semiotic (1959)," presented here, shows that Percy was well ahead of his contemporaries in understanding the scientific and philosophical importance of Peirce's Semeiotic, the Theory of Semeioses. Percy particularly pointed to the experiential importance of "taking the other's meaning." He regarded that common phenomenon as vital, and genuine—a kind of event that behaviorists such as B. F. Skinner or Charles Morris explained away as nothing but a dynamic dyadic causal (or S-R) process. Percy's essay definitively blocks those reductions.