What is the difference between everyday realism and metaphysical realism?

Question

At an everyday level, we seem to subscribe to a from of strong realism which doesn't leave any room for skepticism. We are certain that individuals who hear voices in their heads or who have hallucinations are dysfunctional and something is wrong with their sense data. We can immediately attribute such occurrences to some neurological problem or drug that needs to be cured medically.

Similarly individuals or groups who claim to be communicating with the dead or with extraterrestrials, or with the Valhallic deities, are deemed to be dysfunctional, even if their sense data per se is not faulty. We know for certain that there is something irrational/non-logical about their interpretation of their sense data and that they need to change their worldview.

On an every day level, we are subscribing to a hard realism and some sort of correspondence theory of truth.

And yet at the philosophical level, it is very hard, maybe even impossible to have such epistemic certainty. There are serious challenges to metaphysical realism, scientific realism, the existence of other minds, the existence of matter, etc...and there is also the fact that all observations are theory laden, and that all theories are underdetermined. Skepticism and relativism seem very difficult or impossible to refute.

My questions:

• What is the difference between common sense everyday realism and metaphysical realism?
• If X has consumed LSD (unbeknownst to me) and now sincerely claims that he is flying around the park, I know for certain that the problem is with his perceptual apparatus (even if I might not know the cause of the problem), not with me and him having competing theories about gravity and how each of us perceive the park. Why is such certainty possible?

Answer 1

I think here the difference in certainty is the difference in purpose. We put much more certainty into everyday realism because all we are using it for is practical action. And that indeed requires it, for getting enmeshed in fine points of metaphysical commitments will quickly leave one hungry, injured, and then dead. It is not that there is something "metaphysically wrong" with illusions, delusions and hallucinations, but rather that they often lead to inefficient or even self-detrimental behavior, and that better be nipped in the bud. Berkeley made exactly this point with a "crooked oar" optical illusion at the water surface, remarking that there are no illusions in epistemology.

But with philosophical discourse we are insulated from pragmatic pressures and urgency to act, and have the luxury to dabble in metaphysical musings at leisure, for their own sake, while paying attention to evidence, logic, presuppositions, and other such niceties. Then it turns out that the goalposts between which the practical mind moves with ease of habit have no solid ground connecting them, and there is no tribunal of pragmatic purpose to judge the right from the wrong by efficiency of suggested actions. Realism is hard to defend by these refined standards because these are not the standards that it has evolved to meet.

Berkeley's point was broader, that pragmatic certainties of life leave things wide open on metaphysics. Wittgenstein picked it up, and took it further:"Philosophy may in no way interfere with the actual use of language; it can in the end only describe it... It leaves everything as it is". It is literally vital to reach consensus on using language to coordinate how we act, beyond that it is not so vital. And metaphysical aspects, aspects that "leave everything as it is" open up plenty of room for skepticism and relativism. Wittgenstein's solution is his well known philosophical minimalism: there is no point to these extras because they take words beyond the contexts that give them meaning, and so just juggle empty words:"Philosophy is a battle against the bewitchment of our intelligence by means of language".

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P.S. To the charge that his "esse est percipi" ontology flew in the face of common sense Berkeley replied that it changed nothing common sense had to say in practice, nor did it change the practice itself. Here is from the Third Dialogue between Hylas and Philonous:

"HYLAS. Ask the first man you meet, and he shall tell you, to be perceived is one thing, and to exist is another.

PHILONOUS. I am content, Hylas, to appeal to the common sense of the world for the truth of my notion. Ask the gardener, why he thinks yonder cherry-tree exists in the garden, and he shall tell you, because he sees and feels it; in a word, because he perceives it by his senses. Ask him, why he thinks an orange-tree not to be there, and he shall tell you, because he does not perceive it."

Answer 2

Let's distinguish prima facie justification based on a pragmatist consideration of things actually being the way they seem, and how it seems they relate to other things, in the absence of defeaters from certainty. Everyday realism can operate from prima facie justification... alone, and philosophical/metaphysical realism can be not affirmed with certainty despite recognizing the praxeological utility, perhaps even necessity in some respect(s), of everyday realism. It also depends on what 'real' means; one could be an everyday realist just out of practicality while in the Matrix.