 The precise role of these four faculties is not easy to evaluate on the basis of Aquinas’s limited and scattered remarks, but according to his most prominent account the common sense is what allows us to make cross-modal sensory judgments (seeing something as white and sweet) and to have second-order awareness, for instance “when someone sees that he is seeing” (ST 1a 78.4 ad 2). The imagination—Aquinas uses both imaginatio and phantasia to refer to this faculty—retains images acquired through the external senses. The estimative power perceives what the Arabic tradition referred to as the “intentions” (maʿānī) that lie behind the sensible qualities: for instance, that wolves are dangerous and that straw is useful for nest building. (Aquinas refers to the more sophisticated human capacity for grasping intentions as the cogitative power.) Memory preserves these intentions. All of the internal senses are richly engaged in human cognitive activity, which is to say that the brain—despite not being the power of intellect—plays a critical role in human cognition.