 (iii) In recent years the term wave functional interpretation has been established as the name for the default field interpretation of QFT. Correspondingly, it is the most widely discussed extant proposal; see, e.g., Huggett (2003), Halvorson and Müger (2007), Baker (2009) and Lupher (2010). In effect, it is not very different from proposal (i), and with further assumptions for (i) even identical. However, proposal (ii) phrases things differently and in a very appealing way. The basic idea is that quantized fields should be interpreted completely analogously to quantized one-particle states, just as both result analogously from imposing canonical commutation relations on the non-operator-valued classical quantities. In the case of a quantum mechanical particle, its state can be described by a wave function \(\psi\)(x), which maps positions to probability amplitudes, where \(|\psi(x)|^2\) can be interpreted as the probability for the particle to be measured at position \(x\). For a field, the analogue of positions are classical field configurations \(\phi(x)\), i.e. assignments of field values to points in space. And so, the analogy continues, just as a quantum particle is described by a wave function that maps positions to probabilities (or rather probability amplitudes) for the particle to be measured at \(x\), quantum fields can be understood in terms of wave functionals \(\psi[\phi(x)\)] that map functions to numbers, namely classical field configurations \(\phi(x)\) to probability amplitudes, where \(|\psi[\phi(x)]|^2\) can be interpreted as the probability for a given quantum field system to be found in configuration \(\phi(x)\) when measured. Thus just as a quantum state in ordinary single-particle QM can be interpreted as a superposition of classical localized particle states, the state of a quantum field system, so says the wave functional approach, can be interpreted as a superposition of classical field configurations. And what superpositions mean depends on one’s general interpretation of quantum probabilities (collapse with propensities, Bohmian hidden variables, branching Everettian many-worlds,…). In practice, however, QFT is hardly ever represented in wave functional space because usually there is little interest in measuring field configurations. Rather, one tries to measures ‘particle’ states and therefore works in Fock space. 