As is shown in the introduction of the book, the notion "illocutionary act" is used with quite a number of essentially different meanings; consequently, it is quite unclear what an "illocutionary act" is actually supposed to be. This problem is the starting point of the thesis. An argument is stated, to the effect that the introduction and use of scholarly terms like, for instance, "illocutionary act", or "performative sentence", is not entirely arbitrary. It is argued that technical terms should not be re-defined without a reason, but in the absence of reasons to the contrary should be used in the way in which they have originally been introduced. This argument is applied to the notion "illocutionary act". John L. Austin is the one who i...