Why Adding Truths Is Not Enough: A Reply to Mizrahi on Progress as Approximation to the Truth

In a recent paper in this journal, entitled ‘Scientific Progress: Why Getting Closer to Truth is Not Enough’ (2017), Moti Mizrahi argues that the view of progress as approximation to the truth or increasing verisimilitude is plainly false. The key premise of his argument is that on such a view of progress, in order to get closer to the truth one only needs to arbitrarily add a true disjunct to a hypothesis or theory. Since quite clearly scientific progress is not a matter of adding true disjuncts to theories, the argument goes, the view of progress as approximation to the truth is untenable. We show that the key premise of Mizrahi’s argument is false: according to verisimilitude-based accounts of progress, adding arbitrary true disjuncts to existing theories is just not enough to get closer to the truth.