Several speech act theorists, including Austin himself, make use of the notion of an illocutionary force. In Austin's original account, the notion remains rather unclear. Some followers of Austin, such as David Holdcroft, view illocutionary force as the property of an utterance to be made with the intention to perform a certain illocutionary act rather than as the successful performance of the act (which is supposed to further require the appropriateness of certain circumstances). According to this conception, the utterance of "I bet you five pounds that it will rain" may well have an illocutionary force even if the addressee doesn't hear it. However, Bach and Harnish assume illocutionary force just in case this or that illocutionary act is actually (successfully) performed. According to this conception, the addressee must have heard and understood that the speaker intends to make a bet with them in order for the utterance to have 'illocutionary force'.
If we adopt the notion of illocutionary force as an aspect of meaning, then it appears that the (intended) 'force' of certain sentences, or utterances, is not quite obvious. If someone says, "It sure is cold in here", there are several different illocutionary acts that might be aimed at by the utterance. The utterer might intend to describe the room, in which case the illocutionary force would be that of 'describing'. But she might also intend to criticise someone who should have kept the room warm. Or it might be meant as a request to someone to close the window. These forces may be interrelated: it may be by way of stating that the temperature is too cold that one criticises someone else. Such a performance of an illocutionary act by means of the performance of another is referred to as an indirect speech act.