"In investigating memory-beliefs, there are certain points which must be borne in mind. In the first place, everything constituting a memory-belief is happening now, not in that past time to which the belief is said to refer. It is not logically necessary to the existence of a memory-belief that the event remembered should have occurred, or even that the past should have existed at all. There is no logical impossibility in the hypothesis that the world sprang into being five minutes ago, exactly as it then was, with a population that ‘remembered’ a wholly unreal past. There is no logically necessary connection between events at different times; therefore nothing that is happening now or will happen in the future can disprove the hypothesis that the world began five minutes ago. Hence the occurrences which are called knowledge of the past are logically independent of the past; they are wholly analysable into present contents, which might, theoretically, be just what they are even if no past had existed."
Russell’s statement is sometimes redeployed by critics of creationism to ridicule the YEC theory of apparent age. I’ve discussed apparent age on several different occasions, so I won’t repeat everything I’ve said on the subject. Instead, I’ll content myself with two observations:
1.Critics of creationism co-opt Russell’s illustration to expose the absurdities of YEC. However, absurdity is context-dependent. As SF buffs know, there are lots of futuristic scenarios in which someone is fed false memories. In those situations, the individual has good reason to suspect or begin to doubt the veridicality of his memories about the "real" world. About his past.
And this is more than hypothetical. Even now it's possible to plant false memories under hypnosis. Or consider the whole "repressed memory" scam which destroyed so many innocent lives (of the accused). Deluded people sincerely claiming to be the victims of ritual satanic abuse, child abuse, &c.
These are limiting cases, but so is the hypothetical under review.
2. Ironically, evolutionary psychology is a prescription for skepticism regarding the external world. As Dawkins put it, in The God Delusion (Houghton Mifflin 2006):
“The human brain runs first-class simulation software. Our eyes don’t present to our brains a faithful photograph of what is out there, or an accurate movie of what is going on through time. Our brains construct a continuously updated model: updated by coded pulses chattering along the optic nerve, but constructed nevertheless…And the same thing works for hearing” (88-90).
“It is useful for our brains to construct notions like solidity and impenetrability, because such notions help us navigate our bodies through a world in which objects—which we call solid—cannot occupy the same space as each other…Our brains are not equipped to imagine what it would be like to be a neutrino passing through a wall, in the vast interstices of which that wall ‘really’ consists. Nor can our understanding cope with what happens when things move at close to the speed of light” (369).
“’Really’ isn’t a word we should use with simple confidence. If a neutrino had a brain which had evolved in neutrino-sized ancestors, it would say that rocks ‘really’ do consist mostly of empty space. We have brains that evolved in medium-sized ancestors, who couldn’t walk through rocks, so our ‘really’ is a ‘really’ in which rocks are solid. ‘Really,’ for an animal, is whatever its brain needs it to be, in order to assist its survival. And because different species live in such different worlds, there will be a troubling variety of ‘reallys’ (371).
“What we see of the real world is not the unvarnished real world but a model of the real world, regulated and adjusted by sense data—a model that is constructed so that it is useful for dealing with the real world. The nature of that model depends on the kind of animal we are” (371).
“The nature of the model is governed by how it is to be used rather than by the sensory modality involved…Once again, the perceptions that we call colours are tools used by our brains to label important distinctions in the outside world. Perceived hues—what philosophers call qualia—have no intrinsic connection with lights of particular wavelengths. They are internal labels that are available to the brain, when it constructs its model of external reality, to make distinctions that are especially salient to the animal concerned” (373).