Thanks to Normblog, I have seen Terry Eagleton’s recent interview on matters of religion, in which he is reported as saying:

All performatives imply propositions.  There’s no point in my operating a performative like, say, promising, or cursing, unless I have certain beliefs about the nature of reality: that there is indeed such an institution as promising, that I am able to perform it, and so on.  The performative and the propositional work into each other.

Before commenting on the substance here (ie, religion), some words on Eagleton’s evident mis-understanding of speech act theory and the philosophy of language, a mis-understanding that should have been clear if he tested his words against his own experiences of life.  His statement concerns performatives — utterances which potentially change the state of the world by their being uttered.  Examples include promises, commands, threats, entreaties, prayers, various legal declarations (eg, that a certain couple are now wed),  etc.  But mere propositional statements (that some description of the world is true) may also change the state of the world by the mere fact of being uttered.
First sentence:  “All performatives imply propositions.”  Well, no, Professor E., not at all.  All rationally-uttered, effectively-executed performatives may be used by rational observers to infer propositions.   But different participants and observers in a dialog (speaker, intended audience, over-hearers) may infer different propositions from the very same utterance.  Worse than that, none, some, or indeed all of these inferred propositions may be true.   All manner of propositional content (including none, some and lots) may be intended to be stated or believed by the speaker of a performative utterance, even when that utterance is not effective in changing the state of the world.   Moreover, utterances which change the state of the world may do so in ways not intended or even not predicted by the speaker.
Even when an utterance is itself just a proposition and not intended to change the state of the world, inferring what proposition the speaker intended to state and — a separate question, this — what propositions are true as a result of the utterance, are non-trivial reasoning tasks with the possibility of no definitive solutions, as this example makes clear.
Second sentence:  “There’s no point in my operating a performative like, say, promising, or cursing, unless I have certain beliefs about the nature of reality: that there is indeed such an institution as promising, that I am able to perform it, and so on.”   This statement too is in error.    First, it only makes sense if it applies to rational speakers of performatives (eg, those seeking to achieve some goal), since performatives may be uttered for any reasons or for none at all.   Otherwise, parrots would be allowed to be speakers of performatives.   Second, malicious or deceiving or whimsical speakers may have goals, for which performative utterances not based on reality may be very effective and thus appropriate.  Third, even if we assume a speaker is not malicious, whimsical or being intentionally-deceptive, he or she may make a performative utterance in order to FORM a belief about reality, rather than starting from one.  I may promise you to do some task in order to find out if you desire that task to be done, or to discover if that task be feasible, or to discover if you believe that task to be feasible, or to discover if you are willing to indicate to me that you believe that task to be feasible, or to discover if you are willing to let me think that you believe that task to be feasible, or to allow you to form the belief that you have led me to believe that you believe that task to be feasible, and so on, ad infinitum.
Third sentence: “The performative and the propositional work into each other.”  They may do so, but not necessarily.  As the analysis above makes clear, there is no necessary connection between a performative utterance and any particular proposition believed by the speaker or by the intended hearer, or by any over-hearer.  How could there be such a necessary connection when an infinite number of propositions may be validly inferred from any performative utterance, as I just showed?
So three erroneous statements in three sentences:   Quite an achievement!   I guess some charitable allowance should be given for the fact that these remarks were in a spoken interview and presumably made off-the-cuff.  But one wonders if the good Prof. E. has ever played poker or bridge, or ever negotiated with a plumber, or ever been in business, or ever instructed any recalcitrant child to do something they don’t wish to.
POSTSCRIPT (ADDED 2012-04-23):  And here is a sad instance of the failure of the speakers and hearers of performative speech acts to infer the same propositions.