Descartes had a sophisticated theory of the mind and mental representation. Notoriously he claimed that sensations systematically misrepresent extra-mental reality and he expressed his view by calling sensations "materially false ideas." Unfortunately, Descartes never gave an explicit explanation of how misrepresentation occurs. Various attempts have been made to illuminate this Cartesian problem by appeal to current internalist, causal and teleofunctional accounts of conceptual content. For example, it has been claimed for Descartes that the biological function of sensations explains both why sensations represent what they do (i.e., their referential content) and why they represent their objects the way they do (i.e., their presentational content). Although this teleofunctional account of Cartesian sensations has the advantage of dissolving his problem of misrepresentation (because sensations turn out to be "materially true"), I argue it is false and besides unattributable to Descartes for textual reasons.