 If the being were allowed to have senses of sound in addition to smell, different, simultaneously experienced sounds would likewise be experienced by it as one noise, but Condillac supposed that any sound would be too different from any simultaneously occurring taste for the two to be amalgamated, as long as either one had once been experienced on its own. Thus, a being endowed with senses of both smell and hearing would experience itself as being both a smell and a sound, and so would experience itself as having a double existence (Treatise I.ix.3–4). It would not, however, necessarily experience itself as being two things at once, at least not if we take the term “thing” to refer to substances. Condillac claimed that, were each particular smell only ever experienced in conjunction with just one particular sound, and vice versa, the two would not be thought of as distinct things or substances, even though they would be distinguished from one another. Instead, the smell would be experienced as having a sound and the sound as having a scent. Otherwise put, each would play the role of property to the other. This is all that there ever is to our concept of substance, insofar as that concept has any meaning at all and is not simply a meaningless word invented by philosophers. Substance is not some substratum in which properties inhere, but a collection of sensations or qualities or properties commonly observed to occur together (Treatise I.xii.3, III.iv.2).