Panpsychism is a monistic metaphysical position that holds that mental and physical are two aspects of the same substance, where 'mental' is typically synonymous with consciousness. P. comes in several forms, ranging from blatant idealism to emergent materialism to dodgy interpretations of quantum mechanics. Modern versions of A. N. Whitehead's extensive theory, now dubbed 'panexperientialism' and partially integrated with QM, are (IMO) the most convincing of the lot, not to mention some of the most elegant and profound systems philosophy (and occasionally science) has produced.