Hey Sarkus! Good thread! I missed it earlier because I was angry (not at you) and kind of avoiding Sciforums. So I missed out on your very good thread. (My fault.)
What is the philosophical nature of "truth"? Is it objective, or subjective, or both/either? What can be considered true/false, e.g. are facts "true", or are only propositions true or false?
The way that I look at it, there are objective states of affairs, things that exist regardless of whether any sentient being is aware of them and regardless of what any sentient being thinks about them. Examples might include 'geological' features and events on Mars, Titan, or a billion (to the billionth power) exoplanets. I call these states of affairs 'objective facts'. Describing and understanding them is the province of the natural sciences.
Obviously there are problem cases, such as abstract facts such as those found in mathematics or the laws of physics. There arguably might be social or psychological facts that depend crucially on what people think. There are potential facts such as fragility. A fragile object is subject to breakage when dropped, even if it is never dropped. There are possibilities and all kinds of modal stuff.
And truth, as I see it, is a property of propositions. It is a property of how we think or speak about facts. Explaining what that truth-property is has proven difficult. Generally speaking, I'm inclined to accept a correspondence theory of truth in most cases. Explaining precisely what propositions are and how a proposition can correspond to a fact is difficult, but it's the best I've got at the moment.
If truth is that (a proposition or otherwise) which corresponds to reality, does this just push the question back to "what is reality?" and whether there is an objective and subjective reality, etc?
Yes. There are metaphysical questions (what is reality?) and epistemological questions (how can beings like us know what is real?). Assuming that truth is correpondence of our propositions with reality, how can we ever know that such a correspondence exists and truth pertains? Wouldn't that require some kind of "God's-eye view" able to perceive the supposed correspondence from outside, so to speak, so as to judge it?
Are there different kinds of "truth" - e.g. scientific truths, personal truths, normative truths, etc?
Lots of people speak as if that was the case. I'm not convinced though.
Does opinion matter when considering whether something is true or not?
Sure. Typically we are biased towards believing things that we want to be true. That's the human condition I guess.
I would suggest that most people's view of truth starts (and maybe ends?) with the Correspondence Theory, the notion that truth corresponds with a fact, or some reality. This was a view held and promoted by Betrand Russell et al.
There are competitive theories, such as the Coherence Theory of truth, such that a truth is such that coheres with a set of beliefs. It ultimately seems to resolve into relativism, and with a "true for me, not true for you" type of truth - i.e. subjective.
Mathematical and some of the other abstract truths might arguably be better understood as coherence than correspondence. But I'm pretty solidly in the correspondence camp, I guess.
There is the Identity theory, where a propositions are not true if they correspond with fact, but are facts themselves, and there are other theories of truth out there in the philosophical ether.
That might conceivably be how mathematical truth works.
A further question of interest crossed my path, that one may like to wade into
:
"Is there any factual truth to moral propositions?
How can the idea of objective moral truths be made consistent with a correspondence theory of truth and fit into a physicalist sort of 'scientific' realism?"
My own tendency is to deny that moral propositions express moral truths. Mainly because I don't believe that objective moral facts exist. That being said, one can arguably express truths about what individuals or particular groups of people say and do regarding morality. Their speech and behavior might constitute objective facts to which propositions might correspond.
But ultimately, when we ask whether whatever this individual or group says is 'good'
really is good, I don't think that there's any truth to the matter. Our judgments in that regard are more a matter of our own feelings and intuitions. It might be possible to hypothesize about how these innate moral intuitions evolved in humans (evolutionary ethics is popular these days) so as to promote people working as social groups, but that still doesn't address whether what has evolved is really
right and
good.