ABSTRACT
In 'Of our Complex Ideas of Substance', John Locke addresses the much-contested definition of substratum appears, a supposed but unknown support of the Qualities. Most significant in this definition are the dual qualifiers that Locke uses: supposed and unknown. This chapter examines this two-qualifier definition, illuminating the historical and philosophical significance. It argues that the bare substratum reading deprives Locke's substratum of the active role, performed by its own positively-natured property, in unifying the bundle of qualities into a single substance. The role realizer is a particular constitution of the insensible particles, which is the subject matter of what Locke refers to as 'experimental philosophy', which the author would now call 'natural sciences'. Indeed, there are two dimensions in Locke's account of substratum: experimental and speculative. The idea of the mind that Locke frequently refers to in parallel with that of the body is concerned with cognitive or volitional functions.
