 Why think that a modular view of the mind should allow for diachronic penetration? When Fodor allows for diachronic penetration, he does so because the alternative is to say that all modular systems are specified endogenously (1984: 39). Fodor admits that this alternative would be too extreme, and he points out, for instance, that children learn something from hearing a language. In other words, the modules for language are not just specified endogenously. However, Fodor is conservative about the scope of diachronic penetration, suggesting that it may only happen within strict limits, perhaps limits that are themselves endogenously defined (1984: 39–40).