According to Karen Neander’s causal-informational teleosemantics, the contents of perceptual states depend on the etiological response functions of sensory-perceptual systems. In this paper, I argue that this theory is, despite its virtues, unable to explain how humans and other animals are capable of perceiving properties with which no sensory-perceptual system has ever been confronted. After rejecting Neander’s own proposal in terms of second-order similarity and a proposal inspired by Ruth Millikan in terms of simplicity, I offer a solution which equates (...) functions with manifestations of dispositions that made a difference to evolutionary success. My suggestion is able to generate determinate and plausible contents for new perceptual states while still preserving the idea that etiological functions explain evolutionary success. (shrink)