The "meaning theory" isn't quite what I"m getting at - the best name would probably be the "algorithm theory." It goes like this: there is some algorithm that determines whether an agent thinks X ought to happen - which we, as humans communicating, can agree means something or other general about the agent's moral thoughts or decision-making algorithm. This algorithm for sorting "ought" is like a definition - a definition is something we can use to sort objects. But it's not like any old definition - this definition cannot be guaranteed to be smaller than the brain of the agent.

Or to put it another way, by "definition" I mean the full specification of a cloud in idea-space.

So even when it's possible to use "ought" in the same general way to refer to some part of an agent, this only refers to the fuller algorithm inside an agent. And though these simple definitions are useful for communication, inside peoples' heads there is not a simple pointer like "ought not -> blameworthy" - there is a complicated bunch of neurons that takes in sensory information and outputs moral decisions. There is no reason why this complicated bunch of neurons should be exactly identical for each person.

Anyhow, back to some sort of topic:
You seem to be saying that Parfit is not claiming his theory as any sort of One True theory. Is this accurate? The reviews implied it, but maybe I read wrong.