Józef Maria Bocheński introduced an important distinction between deontic and epistemic authority. A typical example of epistemic authority is the relation of a teacher to his students; a typical example of deontic authority is the relation between an employer and his employee. The difference between the two lies in domains of authority: declarative sentences make up the domain in the case of epistemic authority, orders—in the domain of deontic authority. In the article, I analyze in detail the concepts of the two kinds of authority and propose some new explications. The concept of epistemic authority is distinguished from the concept of infallibility and expertise; and the concept of deontic authority is distinguished from the concept of sovereign. I interpret various kinds of deontic authority in the light of the theory of imperative sentences. The concepts of gradation and de-gradation of authority are introduced and explicated.