This paper centers around the notion that internal, mental representations are grounded in structural similarity, i.e., that they are so-called S-representations. We show how S-representations may be causally relevant and argue that they are distinct from mere detectors. First, using the neomechanist theory of explanation and the interventionist account of causal relevance, we provide a precise interpretation of the claim that in S-representations, structural similarity serves as a "fuel of success", i.e., a relation that is exploitable for the representation using system. Then, we discuss crucial differences between S-representations and indicators or detectors, showing that-contrary to claims made in the literature-there is an important theoretical distinction to be drawn between the two.
Keywords: Antirepresentationalism; Interventionism about causation; Mechanistic explanation; Mental models; Mental representation; S-representation.