[darkmighty]

Of course it's not a tautology. There's no boundless recursivity -- you stop at a point wherein you define your utility function.

What I mean by the utility function being arbitrary is there is no way to derive it from within utility theory, or within mathematics for that matter. In this sense the laws of physics are arbitrary; what you define as good principles of utility are also arbitrary, but that doesn't make them useless -- in fact the stochastic version of the theory is widely applied in decision making and artificial intelligence. It let's you scrutinize the basic principles and act consistently based on that. Not unlike other mathematical tools, it's a way to find the best course of action given a small set of assumptions, and not more than that (i.e. doesn't provide a way to find the assumptions, because it's impossible).

Ultimately we're just certain animals of a species, and things like happiness, ethics, morality, are the outcome of our traits and can't be defined in a vacuum.

As noted, there's also the equality interesting reverse utility theory -- that is, finding utility functions that approximately match our choices. It's just as useful, it shows clearly how we instinctively prioritize things like money, time, feelings; I think it's all quite valuable analysis.