 In his famous defence of negative liberty, Berlin insisted that values or ends are plural, and further, the pursuit of one end necessarily implies that other ends will not be achieved. In this sense ends collide. In economic terms, the pursuit of one end entails opportunity costs: foregone pursuits which cannot be impersonally shown to be less worthy. There is no interpersonally justifiable way to rank the ends, and no way to achieve them all. Each person must devote herself to some ends at the cost of ignoring others. For the pluralist, then, autonomy, perfection or development are not necessarily ranked higher than hedonistic pleasures, environmental preservation or economic equality. All compete for our allegiance, but because they are incommensurable, no choice can be interpersonally justified.