It is a common idea that a proper engagement with and understanding of a work of art requires actual experience of the work itself. According to this view, one will miss something, which it might not be possible to convey in words, if one simply reads an accurate description of, for example, Richard Wagner’s Tannhäuser, Ludovico Ariosto’s Orlando Furioso, or Sakata Tōjūrō’s wagata style of acting, without, respectively, listening, reading, or watching them. Philosophers have gone further and assumed that, in addition to engagement and understanding, aesthetic judgments should be based only on first-hand experience, as well. In fact, various accounts of the structure of our aesthetic judgments take for granted different versions of the following principle: acquaintance with an object is a prerequisite for expressing a proper aesthetic judgment on it. Recently, this principle has been called sometimes the acquaintance principle or principle of acquaintance (PA). With respect to judgments on works of art, the PA implies that, if a person does not perceive a work of art with her own senses, she will not be able to express a proper aesthetic judgment on it. In this paper, I identify the possible merits of this principle and discuss a number of putative counterexamples that are derived from conceptual art. In the first section, I discuss various recent reformulations of the PA. In the second section, I introduce a number of issues from the contemporary discussion on conceptual art and specify why works belonging to this tradition have been taken as counterexamples to the PA. In the third section, I advance various considerations to the effect that works of conceptual art do not pose particular problems to the PA. In the fourth section, I propose two refinements of the PA in terms of the notion of “artistic medium” and argue that my reformulations are truisms and can vindicate our intuitions about the appreciation of conceptual art.