We often use the verb "know" to form utterances which look like imperatives (like "You should know that p"). But while people can choose to believe in certain subject-matter proposed in an utterance they cannot literally choose to know that subject-matter, because to know means not only to be in certain state of mind but also to be in certain relation to the world, and we cannot literally choose to be or not to be in corresponding relation. We cannot do it because being in such state is partly determined by facts of the world. Then "You should know that..." may be an imperative? Or cannot they? The semantic meaning of utterances of the form "You should know..." is investigated in this article, and the author shows that in spite of human inability to choose to make oneself knowing what is required to be known by such imperatives they still may be treated as partial imperatives.