Defining reality as we perceive it . . .
. . is the job of Science. Since we appear to have a sort of consensus reality, consistency should be pretty good, as has been established by scientific experiment.
Though two people may have somewhat different perceptions of the color yellow, they can generally agree without too much arguement that it is the color yellow. Other critters may or may not have an equivalent of yellow,
Our perception may differ from scientific "fact", and that may be our fault, or the fault of science. For instance, you can light a room with a bright neon bulb. Neon has a very sharp orange emission line, but is just about always contaminated with some Argon, which provides a violet line. With these two lines, most people can see pretty much full color, even though "science" would expect not.
The problem here is that scientific instruments aren't perceiving color by the same method as humans do. That a human can extrapolate all the colors from two lines indicates there's a lot of room for differing interpretation from critter to critter.
That science can reasonably define the reality we perceive does not in any way preclude there being stuff outside of or incompatible with our mode of perception. Science, being entirely perceptual, would have a real hard time detecting that, or proving or disproving its existance.
Since ours is apparently a consensus reality, you likely check your reality against the consensus pretty continuously, and it should match pretty well. If it doesn't, that's reason for concern. Your perception may not be wrong, but you'd better check it out pretty carefully. Unfortunately, most who "go off the deep end" do not have the presence of mind to do this checking, and just presume everyone else is denying obvious reality for some obtuse purpose.
This does not apply to political consensus, where the consensus perception is almost always completely wrong. The mistake you can easily make, though, is in thinking that since they are wrong, you are right. You can be equally, or even more wrong, just wrong in a different way. Some Vietnam protestors later realized this, to some distress.
