Considering Descartes' malicious demon idea, is it possible that we could be manipulated in such a way so as all our beliefs are false? I'm thinking that we'd already need some true beliefs in order to have false ones. To be fooled into thinking that pig beards are shorter on Tuesdays I'd have to have true beliefs about pigs, beards, length, and Tuesdays for example. Can I infer then that the overwhelming majority of our beliefs must be true?

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This kind of argument has been made by many different philosophers. Two that come immediately to mind are Ludwig Wittgenstein and Donald Davidson. Their considerations are broadly along the lines of: To have any beliefs at all about pigs, beards, etc, I must have some (mostly?) true beliefs about them. For Davidson, the argument involves considerations about what he calls"radical interpretation", the process of making sense of anotherthinker. But that just seems to me to answer the wrong question. The issue isn't about what's involved in making sense of someone. Maybe you do have to agree with the person about a lot of things to do that. The issue concerns what it is to have beliefs.

Jerry Fodor has written at length about a great conflict between broadly "pragmatist" theories about the contents of beliefs and, uhh, non-pragmatist theories. According to Fodor's view, for example, being able to have beliefs about pigs involves being in the right kind of causal relation with pigs, and there isn't any obvious reason that being in that kind of causal relation should require you to have mostly true beliefs about pigs or, indeed, any true beliefs about pigs. Maybe you're wrongly convinced that you are a brain in a vat, for example, and that there aren't really any pigs---though of course you play along with the evil demon by acting as if there are.

As Richard suggests, the success or failure of arguments of this sort depends on the success or failure of arguments about the nature of the content of our beliefs and other thoughts.

So, for example, in his later writings Davidson made clear that his account of (as he called it) the veridicality of belief--his account of why by their very nature the vast majority of our beliefs must be true--depends on his defense of a version of a doctrine that philosophers call "externalism," and which asserts that the content of our beliefs and other thoughts is (in part) determined by the very external objects those thoughts purport to be about.

If this view of the content of our beliefs is correct, then the thought that the world might be completely different from what we perceive it and believe it to be would be mistaken in a rather strong sense: despite appearances, massive error of that would turn out to be unintelligible.

Understanding whether or not any one view of content is correct is a complicated affair that involves many philosophical challenges. So, exploring the type of argument you raise in your question requires quite a bit of work. If you are interested in knowing more about Davidson's argument about the veridicality of belief, a good place to start is with the work of his teacher and mentor, Quine. Even though Quine's and Davidson's accounts of the nature of the content of our belief are quite different from each other, Quine's text *Word and Object* is a fairly accessible starting place that lays out some ideas that are key to Davidson's account.

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