There is no “ first ” quantization

The appearance of spinor fields as operators or arguments of field functionals in quantum field theory is often regarded as a second quantization, since fermion wave functions were themselves discovered by quantizing mass points (" particles "). I argue that this language, though reflecting the historical development, is misleading. Field amplitudes always represent the true physical variables (in quantum theory the arguments of a fundamental wave functional), including fields which never appear classical, while apparent particles are no more than the result of decoherence in the measuring device, without playing any fundamental rôle in the theory or its interpretation. A remark on gauge fields is added. 1. Introduction. Decoherence theory [1] allows us, in an appropriate sense, to derive classical properties in terms of universal quantum concepts. Classical properties include clicks of a detector or spots on a plate, phenomena which represent outcomes of measurements, and which seem to indicate the presence of particles. Particle concepts are therefore usually presumed for a " quantization " procedure, and for the probability interpretation of scattering amplitudes and other quantum states. Relativity requires quantum field theory, where single particle wave functions , together with classical fields, now appear as arguments of field func-tionals representing the quantum states. The resulting occupation number representation of free fields (coupled oscillators) naturally explains " particle permutations " as identity operations, a situation that has deeper consequences than a mere particle indistinguishability. The combination of these two conclusions suggests to abondon a primor-dial particle concept completely, and to replace it with fields only. While this is indeed what has always been done in the formalism of quantum field