  There is still another feature which is commonly taken to be pivotal for the particle concept, namely that particles are localizable in space. While it is clear from classical physics already that the requirement of localizability need not refer to point-like localization, we will see that even localizability in an arbitrarily large but still finite region can be a strong condition for quantum particles. Bain (2011) argues that the classical notions of localizability and countability are inappropriate requirements for particles if one is considering a relativistic theory such as QFT. 