Thomas Reid argues that both perception and memory involve a conception of an object and usually cause a corresponding belief. According to defenders of the constitutive interpretation, such as Rebecca Copenhaver, the belief is constitutive of acts of perception and memory. I instead argue for a causal interpretation: although in normal circumstances perceiving and remembering cause a corresponding belief, the belief is not constitutive of perception or memory. Copenhaver's strongest argument for the constitutive interpretation is that perception essentially represents objects as present, while memory essentially represents objects as past; since such tense markers can only occur within the beliefs, the beliefs must be an essential aspect of perception and memory. I argue, in contrast, that temporal markers are contained in our conceptions of objects, so beliefs do not play an essential role in distinguishing between perception and memory. Such a reading presupposes a “thick” interpretation of what Reid means by a conception, according to which a Reidian conception is a mode of presentation of the object apprehended.