((I left this comment on a post in electric agora. I'm posting it here for the record.))
I went a bit metaphysical there on you for a bit but I do think that the sceptically vulnerable physical can get confused with it.. In good light and not having ingested psychotropic substances and facing the right way I can say with assurance - ‘there is an tree in the yard’. As a brain in a vat and as a subject trapped in a computer simulation I could say the same thing with the same assurance and be wrong. What would ‘wrong’ mean in this case? Is it not parasitic on the true ‘wrong’, the one that is open to correction? All observations are subject to determined scepticism and we can only stay calm and carry on.
However metaphysical realism is different. It relies on their being an ontological substratum which unites Subject and Object. This is the approach of Platonic, Aristotelian and Vedantic philosophy. It is coherent with the project of critical realism in the physical sense. We accept the truth of our observations as a default assumption. We could be wrong though, but this ‘wrong’ is a true ‘wrong’ i.e. one connected to the metaphysical reality of the unity of the substratum.
My point is that realism which tries to establish itself solely in the domain of observation is not on the ‘wrong’ track if you will forgive a paradox.