The issue of time-awareness presents a critical challenge for empiricism: if temporal properties are not directly perceived, how do we become aware of them? A unique empiricist account of time-awareness suggested by Hume's comments on time in the Treatise avoids the problems characteristic of other empiricist accounts. Hume's theory, however, has some counter-intuitive consequences. The failure of empiricists to come up with a defensible theory of time-awareness lends prima facie support to a non-empiricist theory of ideas.