[johnbernier]

In computer science we typically count from zero, not from one. So even though a category has two different sorts of entities: objects and morphisms, since we count from zero, ordinary categories are one-dimensional. Objects are zero dimensional and morphisms are one dimensional.

Since you are concerned with sets and functions, the following analogy is helpful to build your intuition for the subject.

Dimension 0: sets

Dimension 1: functions

Dimension 2: commutative squares

Dimension 3: commutative cubes

The majority of categories, expressed in terms of structured sets and functions, never touch on the second dimension. That is the domain of 2-categories, which although they have three types of elements are nonetheless considered to be two dimensional because we count from zero. That is also where commutative squares come in to play, because as you can imagine squares are quite obviously two dimensional.

Functions are 1-dimensional lines or arrows from one place to another. Sets are more analogous to points then anything else, and so naive set theory is zero dimensional. But I think you have the wrong question. You should ask the opposite question: what if functions can be re-expressed or founded on higher dimensional category theory?