A hearer of (23a) is given immediate access to his general knowledge about turning keys and starting cars, part of a bunch of strongly held, frequently used assumptions about people's interaction with cars. The cost of accessing these sorts of assumption is negligible and they represent the kinds of relations which are quite standardly relevant to us (have contextual effects) since they enable us to make sense of events in the word, in particular human behaviour, and to predict that behaviour and its consequences. There is not a lot more to be said about this example, artificially