 This schema leaves open how neural types are individuated. We may bypass that question here, because neural individuation of Mentalese types finds no proponents in the contemporary literature. The main reason is that it conflicts with    multiple realizability:   the doctrine that a single mental state type can be realized by physical systems that are wildly heterogeneous when described in physical, biological, or neuroscientific terms. Putnam (1967) introduced multiple realizability as evidence against the   mind/brain identity theory,  which asserts that mental state types are brain state types. Fodor (1975: 13–25) further developed the multiple realizability argument, presenting it as foundational to LOTH. Although the multiple realizability argument has subsequently been challenged (Polger 2004), LOT theorists widely agree that we should not individuate Mentalese types in neural terms.