 This definition, though, also poses a difficulty. In recent decades, it has been thought to imply that lekta subsist only in connection with the representations of rational animals – something not stated explicitly in our reports – even though this would have problematic consequences: it would imply that nonrational animals and indeed very young humans, before they develop reason, would either paradoxically have representations without any content at all or solely with nonconceptual content that could not be articulated. (For a classic statement of the view, see Frede 1983 [1987], 153–54, 156; for a discussion of the consequences, see Sorabji 1993, 20–28.) Neither the Stoics nor their critics ever mention such consequences, and it would make it difficult, if not impossible, for them to account for animal behavior, much less the emergence of reason itself in humans. They insist that we have no concepts (ennoiai) at birth, comparing the mind to a blank sheet of papyrus, ready to be written upon: it is first inscribed by perceptions and then subsequently, through the sorting and collection of perceptual memories, by experience, issuing in our first natural concepts, from which we can later construct even more complex concepts. Reason only appears later – some sources say at age seven, others at fourteen – when there are sufficient concepts to form a stable, interrelated system (Aetius 4.11.1–4; Plutarch On Common Conceptions 1084f–1085a; Diogenes Laertius VII 53). So on the Stoics’ view, children will possess concepts at some stage before they have reason, since reason emerges from the cumulative acquisition and systematization of concepts, and evidently some of these concepts are formed naturally from perceptions and memories alone, unaided by reason, from which they presumably derive their content at least in part. Since all these states undoubtedly possess content, there is no principled ground for denying analogous content in the case of representations in nonrational animals either, at least for perceptual representations.