The article presents the analysis of a sincerity condition as necessary requirement to successful speech act under the example of J. Searle and R.A. Yuriev's approaches. It is shown that the sincerity condition of the form "S intends to do A" is a necessary condition of doing the speech act of promise, and the rule of sincerity of the form "Promise is to be uttered only if S intends to do A" that is constituting the promise as the speech act is a sufficient condition of understanding (recognition) of that the promise has been uttered. It led to state that J. Searle and R.A. Yuriev's requirements to recognize insincere promises as promises, and, therefore, speech acts, are untenable and wrong.