  Since this line of interpretation seeks to downplay Locke’s agnostic tendencies, one challenge is to account for Locke’s pessimism about the possibility of our knowing real essences. Mandelbaum meets the challenge by confining Locke’s pessimism to the real essences of particular material substances; we are able to know “the general properties possessed by all material substances”, and are ignorant only of the “particular sizes, shapes, number, or motions of the particles which go to make up any specific object”(Mandelbaum 1964, p. 54). A related challenge is to account for Locke’s appeals to superaddition, since prima facie, Locke’s reason for invoking God is that he thinks the corpuscular hypothesis has no resources for explaining the four problematic phenomena. Ayers responds by rejecting Wilson’s divine annexation interpretation of superaddition in favor of a deflationary one. According to Ayers’ “divine architect” interpretation, Locke makes no distinction in etiology by calling a property superadded; he means only that God selected the property with particular care when first creating matter. To diffuse the effect of Locke’s remarks to Stillingfleet, in which Locke appears to embrace action at a distance, Ayers points to Locke’s late manuscript, “The Elements of Natural Philosophy”, interpreting certain passages as referring gravitational effects to an undetectable medium (Ayers 1981, pp. 212–214). This move has been challenged by Stuart. Claiming that the manuscript was probably written for the education of a child, Stuart denies that it could trump Locke’s remarks to Stillingfleet (see Stuart 1998, pp. 378–379).