I recently watched a tv show that produced a line of questioning in my head on the virtue of reality. How do we define reality? What's the difference between reality and a world that is the perfect replication of reality? What would be the difference between the two worlds? Is it truly possible to know when we are living in reality? I guess I'm mostly asking if there is work form past philosophers that I could read on the subject?

A perfect replica of reality would be like reality in all respects. It would contain trees—real trees. It would contain people—real people. It would contain fake butter—real fake butter. And if it were a perfect replica, everything in reality would be in the replica. So in every sense that matters, it would be real.

But I have the feeling you're worried about how you can know that you're not systematically deluded or deceived about more or less everything. This was Descartes' question in Meditations. He thought that there was one thing he couldn't be deceived about: that he was having doubts and therefore that he, the doubter existed.

From there to anything substantial, like trees and people and electrons and burritos is a long way. Descartes thought that just by reasoning about it, he could prove that there's a God who is not a deceiver, and therefore that even though he was no doubt wrong about some things, he wasn't systematically wrong.

Most philosophers don't think his argument was very good. Most philosophers also think that if what you're looking for is some irrefutable philosophical proof, then you're out of luck. And yet most philosophers—none that I know personally— worry about this. There doesn't seem to be much of a reason to take wholesale skepticism about the external world seriously. It could be true, in some weak sense of "could," but that goes for a lot of things that no one takes seriously. (Bertrand Russell's example was the possibility that the work came into existence five minutes ago, looking for all the world as though it had been here since the non-existent-under-that-assumption Big Bang.)

Questions about reality tend to be better the less far they float into the stratosphere. Is that a real Gucci bag or a knock-off? Is that actor in that movie scene really Eksie McWhy or is it her stunt double Aybee Dee? Is the grape flavor in the punch real or a laboratory concoction? Is that a real diamond or a piece of costume jewelry? Questions like that get their grip because they're set against the backdrop of the (perfectly sensible) assumption that we typically know what's what—at least about ordinary stuff and middle-sized dry goods. The farther our questions float away from this sort of grounding, the bigger the risk that there won't be enough air beneath their wings to keep them afloat.

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