 During this period the explanatory remit for theories of attention broadened in two directions. The first move was away from the idea that attention acts on already-received ideas and towards the idea that attention is involved in the initial reception of those ideas. Locke had characterized attention as the registration of already-received ideas into memory. But by 1769, when Henry Home Kames added the appendix of ‘Terms Defined or Explained’ to his Elements of Criticism, attention’s role as a regulator of cognitive input was regarded as definitive of it: