 This interpretation of Locke’s notion of ‘substance in general’ is, however, a matter of controversy. It is contested whether Locke actually believed in substance as a characterless substratum. Although the first quotation above seems to affirm it, Locke also in the same section speaks disparagingly about the idea, comparing it to the notion that the world rests on an elephant, which rests on a tortoise, and so on: in other words, as not constituting a real explanation at all. Michael Ayers (1975, 1991b: 39–50) believes that the only substratum that Locke acknowledges is the unknown—and, Locke thinks, unknowable by us—structure of the minute parts. This is what he elsewhere characterises as the real essence. It is clear from the text that Locke is at least uneasy with the idea of ‘pure substance in general’, but it is less clear whether he feels obliged to accept an idea he dislikes, or whether he rejects it. (For the view that he accepts it, and why, see Bennett 1971 and 1987.)