Abstract: We seem to directly perceive external things. But can we? According to the time-lag argument, we cannot. What we directly perceive happens now. There is a time-lag between our perceptions and the external things we seem to directly perceive; these external things happen in the past; thus, what we directly perceive must be something else, for example, sense-data, and we can only at best indirectly perceive other things.
This paper examines the time-lag argument given contemporary metaphysics. I argue that this argument is not as compelling as it may initially seem. First, it denies that what we directly perceive can ever be what it seems to be; second, it conflicts with the current physical conception of time, relativity theory. This latter point leads to a more general one: the argument's force depends on a particular metaphysical conception on time, presentism, which is controversial in contemporary metaphysics of time. Given the alternative conception, eternalism, the argument is much less compelling. The overall argument of this paper, then, is that, if one wishes to hold that we directly perceive external things, we should subscribe to the latter view of time, i.e., eternalism.