Post-print of a paper to appear in Angelucci, A., Fano, V., Ferretti, G., Galli, G., Graziani, P. and Tarozzi, G. (eds.): Realism and Antirealism in Metaphysics, Science and Language. Festschrift for Mario Alai, Franco Angeli, Milan Alai on Novel Predictions and Explaining the Success of Scientific Theories Matteo Morganti 1. Introduction A guiding thread in Mario Alai’s longstanding research is the exploration of the nature and limits of our knowledge of reality. For at least 20 years now, he has focused specifically on scientific knowledge and the issue of scientific realism versus antirealism, making some rather significant contributions to the advancement of the debate. In particular, with his distinctive rigour and attention to the structure of the argument, Alai has played a key role in defining what is no doubt one of the most convincing, if not THE most convincing, formulations of scientific realism nowadays. Namely, a sort of selective ‘deployment realism’ urging a realist attitude only towards those elements within scientific theories that prove to be responsible for those theories’ unexpected predictions. In this short note, I illustrate (what I take to be) the main components of Alai’s views. Based on the proposed reconstruction, I then suggest a couple of points where Alai’s arguments, and predictivist deployment realism more generally, could be objected to and might benefit from further reflection. 2. Mario Alai’s scientific realism Scientific realism is the thesis that the best philosophical explanation of the success of scientific theories is that they are (approximately) true descriptions of the world. As is well-known, scientific realists have to respond to the antirealist critique based on Laudan-style (Laudan 1981) pessimistic meta-inductions. Even granting realism the status of ‘default’ position, the objection goes, several cases can be pointed at in the history of science in which theories that we now regard as false have nonetheless been successful. Therefore, scientific realism is untenable. Typical realist defences are based on the idea that a realist commitment is in fact still warranted, once it is restricted to those parts of theories that are responsible for their success and have been preserved across theory change. Consider, however, empirical success intended as the ability to account for what has been observed. A constructive empiricist, who is only committed to the empirical adequacy of a