“[Many philosophers of the Academy], in their efforts to puzzle the minds of their hearers, resort to such paradoxes, and are so fertile in inventing plausibilities, that they wonder whether or not it is possible for those in Athens to smell eggs roasted in Ephesus, and are in doubt whether all the time they are discussing the matter the Academy they are not lying in their beds at home and composing this discourse in a dream… From this excessive love of paradox they have brought all philosophy into disrepute… They have implanted such a passion in the minds of our young men that they never give even a thought to the ethical and political questions that really benefit students of philosophy, but spend their lives in the vain attempt to invent useless absurdities.”— Polybius, 200-118 B.C.
“Nothing is more dangerous to reason than the flights of the imagination, and nothing has been the occasion of more mistakes among philosophers.”— David Hume
Human beings are adept at imagining things. This is good not only for things like great art, but also for science, as it is often the case that our ability to imagine what could conceivably cause something is just what we needed in order to find the right path for discovering what is actually causing it.
Furthermore, all consciousness in our universe, to be real, requires causal mediation between object and observer: we don’t “directly” perceive a coffee mug as a “thing-in-itself”, but rather, the photons of light discretely strike our individual visual receptors, these responses are physically transmitted to the brain, which somehow integrates them such that we perceive the coffee mug as an entity. (Something similar happens for every sensory modality.) Even were it the case that our consciousness magically received such inputs “directly”, the transmission of them is also causally mediated: the photons are transmitted; even physical touch is transmitted, albeit across a very short distance. There is therefore no way to guarantee that there is not something just beyond our own physical locale and manipulating all the stimulus we receive from the outside. Does the lack not only of a guarantee but of any possibility of one mean that there “might possibly” be such?
In other words, does the fact that something we imagine is logically consistent with what we know about the universe also mean that it is actually possible?
Consider this question: If I ask a random person “Can pigs fly?” and they say “No”, do I know what they mean? Some people, when they say “No”, mean “No” (i.e. absolutely not); and others mean something on a sliding scale of “unlikely” – since they can imagine that pigs can fly they wouldn’t rule it out. To make matters more uncertain, some people will, in the space of one conversation, convert from the type that says “No” to the type that says “unlikely.”
Suppose I ask the question differently: “Is there any reason to believe that pigs can fly?” Here we might get (1) “No”, or (2) “Yes, and here are some reasons”, or (3) “Yes, I can imagine someone having reasons (and here are none)”.
Should we believe that something is possible even when we have no reason to? Should being able to imagine something count as a reason to believe it?
Note that the “should” in these questions imply that this is a moral question. Should you believe that your loved one possibly committed a heinous act, merely because you can imagine it (and here I mean imagine in the foregoing sense of pure imagination, not in the sense of putting together pieces of actual evidence)? Should a court of law allow they might be guilty because you testify “Yes, I can imagine them committing an atrocity, so as far as I’m concerned they might have done so”?
In other words, should experience govern how you choose your words and meaning, or should mere powers of imagination govern them? What policy is most wise? Is wisdom rooted in experience, or in intellectual flights of fancy?
Wisdom consists not in taking the easy path of not knowing anything (an attribute in common with rocks), but in knowing what to believe and what to doubt. It consists in making firm conclusions where the evidence warrants, and yet remaining, in principle, open to arguments that these conclusions are wrong. It consists in recognizing when we have erred and then in revising our posture concerning related conclusions. We must be honest with ourselves, and if we find a pattern of making serious errors, we should temper our character to be more humble in the future; and if we find a pattern of veracity, we should foster our character to be more fierce, bold, and courageous in standing for what we know to be true and right.
Regarding (2), because human beings are so imaginative, there is a potentially unlimited supply of alleged reasons for why we might be living in a computer simulation. We are in principle open to hearing these arguments ad nauseam and assessing their validity. But note that the question of whether we are living in a computer simulation hinges on whether it is possible to simulate human consciousness in a computer. If we have already refuted that claim, then the question of whether we are living in a simulation is moot.