Every human action is essentially motivated by a normative belief system. To some extent, “drives” and “urges” and “instinct” like laziness, fear, etc. factor in to our behavior, but generally, they only do so to the extent allowed by the intellect. Big, long-term decisions especially are made thoughtfully, and thought is informed by normative belief. An epicurean, for example, would choose to live life simply and make decisions so as to minimize paid. The “rational actor” prefers those things which maximize his or her utility, and chooses accordingly. An arbitrarian attempts to identify the “ideal” alternative, and chooses that.
Arbitrarians often employ arbitrarianism within a framework of other, overarching beliefs, when following the other beliefs leaves ambiguous the question of optimality. A environmentally-conscious bounded rational chooser, for example may go shopping for an armchair: First, they would eliminate from consideration any chairs made out of plastic (because it is non-biodegradable). Next, they would find the chairs that, given their budget constraint, maximized their utility. Then, if there are several chairs left between which the individual is ambivalent, or as part of the utility estimation itself, arbitrarianism would suggest that the shopper pause to consider what the Platonic ideal of an armchair would be like, and buy the chair that most closely resembles it.
The arbitrarian is a big fan of ratings, rankings, operationalizing and objectivity (but not Ayn Rand). Arbitrarianism is often practiced in a weak form. Where the strong form dictates that an individual selects exclusively based on the ideal for the category, practicing arbitrarians tend to employ heuristics, as in rooting for the team with the highest win/payroll ratio or buying the Consumer Reports Best Buy toaster, rather than meditating on what the truly ideal baseball team and toaster are.
In truth, arbitrarianism helps the indecisive decide, and lends a feeling of objectivity to subjective choices. Except for the times when a true ideal can be found, the practicing arbitrarian is just going to pick what he likes, find the one aspect in which that choice outdoes the other options, and assume post-hoc that that aspect is the critical one. At its best, though, arbitrarianism helps us think through tough choices, and serves as a framework in which to consider what really matters in any given decision.