With a convex polytope M in R3, a partially ordered set P(M) is associ
ated whose elements are the vertices, edges, and faces of M ordered by
inclusion. This paper shows that the order dimension of P(M) is exact
ly 4 for every convex polytope M. In fact, the subposet of P(M) determ
ined by the vertices and faces is critical in the sense that deleting
any element leaves a poset of dimension 3.