It is argued that (i) a coherent speech act theory enables us to frame lexical decomposition formulae for performative verbs; (ii) the attempt to do so shows that the notion of perlocutionary effects is central in the description of speech acts; (iii) it is necessary to redefine 'perlocution' in terms of the speaker's intentions; (iv) the lexical decomposition formulae for performative verbs can be re-interpreted as meaning postulates belonging to 'natural logic'.