The basic problem is this, we cannot confirm our senses independent of our senses. i.e. we might all be in a matrix, or having a dream, or be characters in someone else's dream. Can we know that reality exists at all? If we define reality as the physical universe it appears to be, then I don't think we can, however, if we define it slightly looser, maybe as 'the source from which our sensory information originates' then perhaps we can? if this works, and we can know that reality does in fact exist, can we know if our actions truly are effecting it?
we have some philosophy majors here right?