Scientifically speaking, the lesser reality is the greater – assuming that an underworld of physical processes will provide a ‘theory of everything’. But that ‘everything’ is not everything – because experience reveals that a universe which subsists beneath the threshold of self-perception is not the whole thing. However, experience might be confined to a world of its own with no inkling of a ‘bigger picture’ beyond the images that happen to hold our attention.
On the other hand, whatever else reality may or may not be, we can know without further ado that it includes the perception of ourselves thinking. And if our capacity for reflection is the thing that distinguishes our thinking, albeit in the absence of a definitive knowledge of anything else, then at least we can know that thinking exists as a feature of the way things are, though the wider reality may not be tied to the way we think about it.
Even so, this would be sufficient to tell us that we inhabit a sentient reality, as augmented by a power to be, which we can know but incompletely by its instantiation in the vagaries of our understandings. And we can know as much because of the reflective experience of the vagaries of our understandings. Then again, even if we could know everything in terms of ‘something else’ identifiable as the source, we would still need to ask ourselves: have we really identified the whole, or explained the something else?