Merry Christmas

Things have gotten slow around here over the holidays, but we haven't forgotten about you. Regular posting will resume in January.

The Principle of Disagreement

Now the question raised by the mode of disagreement is this: Is the Principle of Disagreement true? And the answer is surely: Yes, the Principle is true. For suppose that it were not true. Then the following could be the case. I recognize that there is a dispute about the authenticity of the Magna Moralia, some holding that the work was written by Aristotle himself and others holding that it is a later counterfeit. I believe, further, that the dispute is still undecided: the parties have not come to any agreement, and no decisive argument or consideration for or against authenticity has yet been advanced. Nevertheless (if the Principle is false) it is rational for me to hold that the work is not authentic. Now it seems clear to me that this is incoherent; for how could it possibly be rational for me to plump for authenticity, thus opting for one side of the dispute, and yet still maintain that the dispute is undecided? If it is rational or warranted for me to decide against authenticity, then I must suppose that whatever warrants my decision also and thereby decides the dispute, which I can therefore no longer hold to be undecided. If, on the contrary, I insist that the disagreement remains undecided, then I cannot consistently suppose that my inclination to reject authenticity, whatever it may be founded upon, has any satisfactory justification; and hence it is not rational for me to reject authenticity.

Of course, I may adopt it as a 'working hypothesis' that the Magna Moralia is a counterfeit. I may act as if the work is spurious – say, by excluding it from my translation of the collected works of Aristotle. But in so acting I am not manifesting any belief that the work is spurious. I am not putting money on the horse. (Moreover, I may perhaps also hold that it is likely or probable that the work will turn out to be spurious. Then I shall indeed hold a belief on the matter – but not a belief which is, in any straightforward way, a party to the disagreement. For the disagreement is not over probabilities but over authenticity.) Thus while recognizing the existence of an unresolved dispute over authenticity, I may yet act as if the work is spurious (and perhaps even take it to be probably spurious); but I cannot rationally believe that it is spurious.

If the putative counter-example to the Principle of Disagreement is incoherent, then any putative counter-example is incoherent. And thus the Principle is true. Then since the Principle on which the mode of disagreement rests is true, the mode does indeed induce suspension of judgment. If I recognize undecided dispute over ?Q, then I must – I rationally must – suspend judgment over the matter.

Jonathan Barnes, The Toils of Scepticism.

I've discussed the principle of disagreement in a previous post here (the first premise), and thought some of you might be interested in Barnes's full argument for it.