Jakobson has argued that Peirce "must be regarded as a genuine and bold forerunner of structural linguistics' (1971:II,565). Indeed the claim that "...modern structuralist thinking has clearly established language as a system of signs, and linguistics as part of the science of signs or semiotic" (1971:II,713),might lend credence to the first proposal. However, the aim of this paper is to determine whether this pronouncement is merely rhetorical or thoroughly substantial. I choose the latter position for two reasons: (1) the compatibility between Jakobson's theory of isomorphism or correlation and Peirce's objective idealism, and, (2) Jakobson's use of Peirce's concept of the interpretant.