 Bach and Harnish think that inference is involved, from the beginning, in the determination of the locutionary act. The next step is to infer the literal illocutionary intentions and from here, in the simplest case, go for the (intended) perlocutionary ones, if any. Roughly, an illocutionary act is literal when its propositional content coincides with the content of the locutionary act, and the force of the former is within the constraints imposed by the latter.