 Along the same lines, Kareem Khalifa claims that abilities are involved in understanding, but holds that they are “especially unspecial” (Khalifa 2017b: 56). For Khalifa, the modal character of abilities is evident in normal scientific practice, because as scientists evaluate explanations on the basis of testing they naturally rule out inadequate explanations and gravitate towards well-supported ones. But evaluating and testing hypotheses in this way does not appear to require anything exotic or special from a psychological point of view, or to entail that the object of understanding is not propositional.