A major focus of ethical argumentation is determining the relative merits of proposed ethical systems. Nevertheless, even the demonstration that a given ethical system was the one most likely to be correct would not establish that an agent should act in accord with that system. Consider, for example, a situation in which the ethical system most likely to be valid is modestly supportive of a certain action, whereas a less plausible system strongly condemns the same action. Should the agent perform (...) the action, arguing that the most plausible system supports doing so, or avoid the action, being conservative about the strong condemnation of it from a less plausible system? I argue that, in general, different ethical frameworks see the ethical world in fundamentally different ways, rendering the comparison of degrees of support and opposition of actions between systems intrinsically invalid. One should indeed choose to act in accord with the most defensible system. I believe that this important topic needs more attention than it has gotten to date. (shrink)