According to S. illocutionary acts, which he regards as the minimal units of linguistic communication, are performed in accordance with constitutive rules (as opposed to regulative ones). Illocutionary acts contain propositions (consisting of a certain reference and a certain predication). The meaning of a speech act is determined by intentions and conventions. S. illustrates how the necessary and sufficient conditions and the rules for the performance of a certain speech act can be formulated (taking into account the foregoing considerations about the nature of illocutionary acts). His example is the act of promising.