Abstract

Two common claims in philosophy are that deep disagreements cannot, in principle, be resolved by argument and that normal disagreements will be resolved by argument. In each claim it is assumed that the parties to the disagreement are rational. I argue that both claims are false. The first fails to take account of refutations. The second fails to recognise the role of conjectures in the dynamics of the growth of knowledge. There is no disagreement such that it is impossible for rational parties to reach agreement by argument; but there is also no disagreement for which parties are rationally required to reach agreement by argument. Given the same evidence, it may be rational for one person to believe a specific proposition and another to believe its negation.