 The previous section indicated the importance of distinguishing between perceiving the present and perceiving something as present. We may perceive as present items that are past. Indeed, given the finite speed of the transmission of both light and sound (and the finite speed of transmission of information from receptors to brain), it seems that we only ever perceive what is past. However, this does not by itself tell us what it is to perceive something as present, rather than as past. Nor does it explain the most striking feature of our experience as-of the present: that it is constantly changing. The passage (or apparent passage) of time is its most striking feature, and any account of our perception of time must account for this aspect of our experience.