I'm not trying to define the terms, just posit a very very simple theory of the form killing is wrong because human life is good. Such a theory would be inferior on its own premises than a very very simple utilitarianism, regardless of whether either or the premise itself is true. As such I oversimplified utilitarianism just as much, but it doesn't matter for the scope of the example.
Edit: in fact, for the purposes of the example it is better if the "deontologist" is wrong about deontology, because it better illustrates how one theory can have g...
I think that this is really a discussion of explanatory power, of which scientific causation is one example. All theories attempt to explain a set of examples. Scientific theories attempt to explain causation in natural phenomena, thus their "explanatory power" is proportional to their predictive power. A unified theory of forces at the planetary and subatomic levels would explain more examples than any do now, thus it would have great explanatory power.
Yet causation isn't the only type of explanatory relationship. Causation implies time and eve...
Here the deontologist is arguing for the principe 'killing is wrong regardless of the consequences' (deontic) but uses a poor justification for which consequentialism is a more reasonable conclusion. So the 'deontologist' is wrong even though his principle cannot be externally verified. I was just (unclearly I see) using this strawman to illustrate how theories could be better and worse at explaining what they attempt to explain without being the sorts of things which can be proven. I will attempt to be clearer in future.