There are (at least) 3 ways to handle the assignment of a truth value to sentences with non-referring subjects, like "The current king of France is bald": 1. Bertrand Russell's solution (as Stephen Maitzen's response points out) was to argue that the subject-predicate (or noun-phrase/verb-phrase) "surface" structure of the sentence was not its real, "deeper", logical structure, and that its truth value could only be determined by examining that logical structure, which would be a conjunction of three propositions: (a) There is at least one current king of France, and (b) there is at most one current king of France, and (c ) he is bald. Because (a) is false, the entire conjunction (and hence the original sentence) is false. It's apparent negation, "The current king of France is not bald", can then be seen to be ambiguous between: (i) It is not the case that the current king of France is bald, i.e.: It is not the case that: (a) & (b) & (c ) and (ii) The current king of...

Peter Smith's use of the deflationary theory of truth to answer this question is just one way of approaching it. Another is to use the correspondence theory of truth. According to (a highly simplified version of) the correspondence theory, truth is a relation between beliefs (or sentences, or propositions) and "reality": A set of beliefs (or sentences, or propositions) is true if and only if they correspond to reality, i.e., iff they "match" or accurately describe reality. Now, a (scientific) theory is just a set of beliefs (or sentences, or propositions). So, a theory is true if and only if it corresponds to reality. But how do we access "reality" so that we can determine if our theories (our beliefs) correspond to it? How can we do the "pattern matching" between our beliefs and reality? One answer is by sense perception (perhaps together with our beliefs about what we perceive). But sense perception is notoriously unreliable (think about optical illusions, for instance). And one...

I'm happy to try to clarify: I don't think that philosophers use facts differently from most non-philosophers. Rather, I think that philosophers use the word 'fact' differently from the way most non-philosophers use it. I think that most non -philosophers use it to mean more or less the same as the expressions 'true sentence', or 'true proposition', or 'true belief'. I think that most philosophers use it to mean more or less the same as the word 'situation' or the phrase 'state of affairs', i.e., a bunch of objects having properties or standing in relations. Used in this way, I don't think it makes sense to call a fact "rational" or "irrational", any more than it makes sense to call, say, the number 3 "beautiful" or to call, say, the color red "odd" (in the sense of not evenly divisible by 2). In this sense, the sentence 'The Earth is round' is true. And the reason that it is true is that there is a fact that corresponds to it, namely, the fact consisting of the object that is the...