1. Student X: Let's go to the movies tonight.

2. Student y: I have to study for an exam.

(1 constitutes a proposal in virtue of its meaning, in particular because of the meaning of "Let's". In general, literal utterances of sentences of this form will constitute proposals, as in: 3. Let's eat pizza tonight or: 4. Let's go ice-skating tonight.)

The utterance of 2 in the context just given would normally constitute a rejection of the proposal, but not in virtue of its meaning. In virtue of its meaning it is simply a statement about Y. Statements of this form do not, in general, constitute rejections of proposals, even in cases in which they are made in response to a proposal. Thus, if Y had said:

5. I have to eat popcorn tonight. or;

6. I have to tie my shoes.

In a normal context, neither of these utterances (5 or 6) would have been a rejection of the proposal.

The question arises, How does X know that the utterance is a rejection of the proposal? and that question is a part of the question, How is it possible for Y to intend or mean the utterance of 2 as a rejection of the proposal?

Let us say that the primary illocutionary act performed in Y's utterance is the rejection of the proposal made by X, and that Y does that by way of performing a secondary illocutionary act of making a statement that he has to prepare for an exam. He performs the secondary illocutionary act by way of uttering a sentence the literal meaning of which is such that its literal utterance constitutes a performance of that illocutionary act. We may, therefore, further say that the secondary illocutionary act is literal; the primary illocutionary act is not literal.

The indirect speech act, performed by Y
the primary illocutionary act	a secondary illocutionary act
rejection of the proposal made by X	making a statement that he has to prepare for an exam
not literal	literal

Let us assume that we know how X understands the literal secondary illocutionary act from the utterance of the sentence. The question is, How does he understand the nonliteral primary illocutionary act from understanding the literal secondary illocutionary act? And that question is part of the larger question, How is it possible for Y to mean the primary illocution when he only utters a sentence that means the secondary illocution, since to mean the primary illocution is (in large part) to intend to produce in X the relevant understanding?

A brief reconstruction of the steps necessary to derive the primary illocution from the literal illocution would go as follows. (In normal conversation, of course, no one would consciously go through the steps involved in this reasoning.)

Step I: I have made a proposal to Y, and in response he has made a statement to the effect that he has to study for an exam (facts about the conversation).

Step 2: I assume that Y is cooperating in the conversation and that therefore his remark is intended to be relevant (principles of conversational cooperation).

Step3: A relevant response must be one of acceptance, rejection, counterproposal, further discussion, etc. (theory of speech acts).

Step 4: But his literal utterance was not one of these, and so was not a relevant response (inference from Steps I and 2).

Step 5: Therefore, he probably means more than he says. Assuming that his remark is relevant, his primary illocutionary point must differ from his literal one (inference from Steps 2 and 4). This step is crucial. Unless a hearer has some inferential strategy for finding out when primary illocutionary points differ from literal illocutionary points, he has no way of understanding indirect illocutionary acts.

Step 6: I know that studying for an exam normally takes a large amount of time relative to a single evening, and I know that going to the movies normally takes a large amount of time relative to a single evening (factual background information).

Step 7: Therefore, he probably cannot both go to the movies and study for an exam in one evening (inference from Step 6).

Step 8: A preparatory condition on the acceptance of a proposal, or on any other commissive, is the ability to perform the act predicated in the propositional content condition (theory of speech acts).

Step 9: Therefore, I know that he has said something that has the consequence that he probably cannot consistently accept the proposal (inference from Steps I, 7, and 8).

Step 10: Therefore, his primary illocutionary point is probably to reject the proposal (inference from Steps 1 and 9).

It may seem somewhat pedantic to set all of this out in 10 steps; but if anything, the example is still underdescribed - I have not, for example, discussed the role of the assumption of sincerity, that attach to various of the steps. Notice, also, that the conclusion is probabilistic. It is and ought to be. This is because the reply does not necessarily constitute a rejection of the proposal. I might have gone on to say: