 Stevenson’s solution to this problem of flux is to provide a dispositional theory of meaning grounded in the causal-historical relations between a sign and the psychological states of those within a linguistic community who have used and reacted to, and continue to use and react to, the sign. For Stevenson, a sign’s meaning is not constituted by its use on an occasion of utterance. Rather, a sign’s meaning is constituted by its power—its “tendency,” “potentiality,” “latent ability,” or “disposition” (1937, 20–22; 1944, 46; 1948a, 158)—to evoke the psychological states of a hearer or to express those of a speaker. The power of an expression, like the purchasing power of a dollar, or the stimulating power of coffee, is to be understood as a complex network of causal relations: