 In a similar fashion but focusing on current theories, Doppelt (2007) claims that realists should confine their commitment to the approximate truth of current best theories, where best theories are those that are both most successful and well established. The asymmetry between current best theories and past ones is such that the success of current theories is of a different kind than the success of past theories. The difference, Doppelt assumes, is so big that the success of current theories can only be explained by assuming that they are approximately true, whereas the explanation of the success of past theories does not require this commitment.