In this article I claim that the Greek philosopher Xenophon, in the third book of his Memorabilia, catalogues six—and perhaps the six—essential and enduring forms of human ambition. Most treatments of ambition depict the phenomenon as monolithic; or, at best, as dichotomous. That is, ambition is understood as a single trait or passion shared by all ambitious people, its manifestations differing only according to circumstance; or, alternatively, as a trait or passion with one good (or high) form and one bad (or base) form. Little attention is paid to an enterprise of cataloguing various types of human beings as embodying distinct forms of ambition, forms which a political community must tolerate or encourage, channel or confront, in different ways. This enterprise is best carried out through the dialectical approach, in which the personality of a particular interlocutor emerges in light of, and in response to, Socratic scrutiny.