The article examines the notions of historicism, stylization and eclecticism using several examples from the history of architectonic and visual arts. The frequency of these phenomena of artistic thinking in different ages is noted. According to the author of the article, it is the triad harmony relations of notions, rather than binary ones, reflect more fully the collisions in the historical development of culture. The author proposes to call the modern era postmillenism. The approach outlined in the article will ultimately allow the above-named terms to be presented as as kind of classification system. This system is preliminary, but it can be used as one of the methodological tools of art studies.