Parfit's claim that Kantianism, contractualism and consequentialism converge would, if true, be a finding of immense importance in normative ethics. It is also important for Parfit's defence of objectivity in ethics. If there are objective normative truths, then people whose judgement is not confused, biased or in some way distorted, and who agree on all the facts, should be able to reach agreement about what we have reason to do, and how we can tell right from wrong. Many people have thought that the deep disagreements between thoughtful Kantians, contractualists and consequentialists are evidence that there is no right answer to such questions. Parfit's response is that there is no such deep disagreement: ''These people are climbing the same mountain on different sides''.
(Peter Singer, "One Mountain," review of On What Matters, by Derek Parfit, The Times Literary Supplement [20 May 2011]: 3-4, at 4)
Note from KBJ: Immense importance? Why would it matter if two or more theories are extensionally equivalent? This doesn't show that there's really just one theory; it shows that two or more theories happen to produce the same results. Philosophically speaking, that is of no importance whatsoever.
Note 2 from KBJ: Singer writes: "If there are objective normative truths, then people whose judgement is not confused, biased or in some way distorted, and who agree on all the facts, should be able to reach agreement about what we have reason to do." It follows from this (by exportation and transposition) that if there is disagreement about what we have reason to do, then either (1) there are no objective normative truths, (2) people's judgment is confused, (3) people's judgment is biased or distorted, or (4) people do not agree on all the facts (i.e., someone is ignorant). The antecedent of this conditional is obviously true (normative disagreement is rampant), so at least one of the four disjuncts must be true. Parfit and Singer refuse to accept the first disjunct ("there are no objective normative truths"), so they are committed to explaining disagreement as either confusion, bias, distortion, or ignorance. I accept the first disjunct: there are no objective normative truths. Is it plausible that the greatest thinkers humanity has produced in over 2,000 years—thinkers such as Aristotle, Aquinas, Hobbes, Hume, Kant, Bentham, Ross, Anscombe, and Rawls—are either confused, biased, or factually ignorant? The very idea is preposterous. The best explanation of normative disagreement is that there are no objective normative truths.
