M. distinguishes two types of conventions: conventions of language, which give rise to the literal meanings of sentences; and conventions of usage, which govern the use of sentences, with their literal meanings, for certain purposes. Indirect speech acts such as 'Can you pass the salt?' are conventional in the second sense. Their use does not involve the computation of the conversational implicatures of the expression, but these implicatures have become conventionally associated with the expression though the expression continues to carry its literal meaning.