> 1) a statement, pattern of behavior, prototype, "first" form, or a main model that other statements, patterns of behavior, and objects copy, emulate, or "merge" into. Informal synonyms frequently used for this definition include "standard example," "basic example," and the longer-form "archetypal example;" mathematical archetypes often appear as "canonical examples."

> 2) the Platonic concept of pure form, believed to embody the fundamental characteristics of a thing.

The confusion between you two seems (to me at least) to fit almost entirely within the difference between those two definition. If you are describing the ideal market maker as essentially performing arbitrage, that seems to fit the second definition pretty well, right?

Meanwhile if wpietri says that most of the work at his believed-to-be-typical example of a market maker was doing non-arbitrage stuff, that'd make sense, right? I guess in most places the main work would be managing the divergence from idealness.