 An initial worry is that the discovery of the logical fact \(E_\textrm{logical}\) does not sound like adding anything to the body of Einstein’s evidence but seems only to make clear the evidential relation between the new theory and the existing, unaugmented body of evidence. If so, there is no new evidence after all. This worry might be addressed by providing a modified version of the Conditionalization Principle, according to which the thing to be conditionalized on is not exactly what one acquires as new evidence but, rather, what one learns. Indeed, it seems to sound natural to say that Einstein learns something nontrivial from his derivations. For more on the difference between learning and acquiring evidence, see Maher (1992: secs 2.1 and 2.3). So this approach to the problem of old evidence is often called logical learning.