Speech acts are utterances whose issuance changes the states of affairs in the world. They were first introduced by J. L. Austin in his seminal book How to Do Things With Words (1962), who divided them into locutionary, illocutionary and perlocutionary acts. Illocutionary acts in particular have, since then, provided a great deal of interest for many philosophers of language. Speech act theories are aimed to explicate how illocutionary acts such as threatening or promising operate and produce an effect. To examine these issues, Austin introduced felicity conditions, which need to be satisfied in order for illocutionary acts to obtain. Felicity conditions that Austin introduced are characterized mostly by convention. Alternatively, conditions that govern illocutionary acts can be viewed as depending mostly upon intention of the participants in the act. In this vein H. P. Grice’s intentionalism provides another way to account for illocutionary acts. Conventionalism and intentionalism are two main approaches in speech act theories in pragmatics. This thesis will examine both of these approaches, as well as the possibility of implementing both of them in a speech act theory. In this way, Austin’s felicity conditions will be evaluated and I will conclude that they are not sufficient for an adequate explanation of illocution because they do not fully acknowledge the importance of intentional elements.