It appears to be widely assumed that to respond rationally to cases of value conflict is in effect to weigh or balance the importance of the values involved, and that weighing or balancing cannot be rational unless there is a common measure of value according to which it proceeds. Understood in the right way, the answer to the question whether or not values are or must all be commensurable in that way will determine what sorts of deliberation are possible and useful. If values are all commensurable in the right way, then one need not devote a lot of attention in deliberation to refining one's conception of them severally, and should better concentrate on weighing how instances of them contribute to the commensurating value (the commensurans, as I will call it). If values are all commensurable in the right way, then deliberation may take on a well-understood and much studied form, that of maximization; while the commensurans itself, if it has the status of being that in terms of which the value of everything else is assessed, will seem a source of value beyond calling into question in deliberation. If values are not so commensurable, then prospects for coping rationally with decisions in which they clash may seem correspondingly dim. Either way, therefore, the commensurability issue lurks as a reef upon which hopes for rational deliberation of ends seem likely to be wrecked: If values are commensurable in the relevant sense, then maximizing good consequences, according to some end taken for granted, is the order of the day; whereas if values are not commensurable in this sense, then rational deliberation seems often impossible.