 Appeals to logical form arose in the context of attempts to say more about this intuitive distinction between impeccable inferences, which invite metaphors of security, and inferences that involve some risk of slipping from truth to falsity. The idea is that some inferences, like (1–3), are structured in a way that confines any risk of error to the premises. The motivations for developing this idea were both practical and theoretical. Experience teaches us that an inference can initially seem more secure than it is; and if we knew which forms of inference are risk-free, that might help us avoid errors. As we’ll see, claims about inference are also intimately connected with claims about the nature of thought and its relation to language.