This essay focuses on Charles S. Peirce’s grammar of representation and its relevance for a logical conception of scientific inquiry. Closely relying on Peirce’s writings, one of his important trichotomies of signs will be discussed in particular: that distinguishing between substitutive signs, or “semes”, informational signs, or “phemes”, and persuasive signs, or “delomes”. According to Peirce, these three categories of signs result from an extension of the traditional division between “terms”, “propositions”, and “arguments” to all signs, understood as the foundational (...) elements with and on which the scientific mind operates. It is shown that such an extended view of logic, conceived as a “semiotic”, or general doctrine of signs, is consistent with Peirce’s metaphysical views on truth and reality. Logic-as-semiotic, and its three corresponding branches of stecheotic, critic, and methodeutic, is thus conceived as a requisite normative trivium for the practice of scientific inquiry, whose purpose is to represent reality truthfully. In the end, we aim to remind that Peirce’s semiotic epistemology must necessarily be contextualized within the frame of his comprehensive philosophy of the scientific “settlement of opinion”. (shrink)