Having rejected attempts to identify the musical work with its performance or with certain conscious experiences, we now have to consider the supposition that the musical work is nothing but its notation or score. This thought will undoubtedly occur to those investigators who regard the postulate entia non sunt multiplicanda praeter necessitatem as an overriding principle—that is, to reduce all types of objects to material things or processes or at worst to certain mental processes. When dealing with objects that others maintain cannot be reduced to the material or the mental, such investigators talk of so-called metaphysical hypostases, regarding these as a grave methodological error. Admittedly the notion of "reduction" has not been fully clarified, but the positivists do not like to acknowledge this, since such reduction often disagrees glaringly with positivism's chief postulate, namely, that one must simply acknowledge all "positive" data of experience. But they themselves unfortunately do not abide by this postulate.