  Yet knowing real essences would not give us any genuine knowledge of how sensations are produced by primary qualities. While corpuscular theorists such as Galileo (The Assayer) sketched a reductive account of our sensations of taste in terms of particles striking our tongues, Locke suggests that any attempt to discover the process’s details will be foiled. For as far as we can imagine, a body, by striking other bodies, is able to produce “nothing but Motion”  [18] (E IV.iii.6, pp. 540–541), and motion may itself be hopelessly obscure, as indicated below. As for shape and size, we can no more imagine how they could figure in the production of sensations than we can imagine how motion could.