reality would be strange if reality relied on human statements and equations. — Andrew4Handel
But - to a large extent it does; property and mortgages and promises all rely on language, and are real. So some things are true in virtue of language, other things not so much.
Truth is complicated. It would be odd if we could set out in a sentence a method or algorithm that could distinguish all true sentences from false sentences. Examples that claim to do this - coherence and correspondence and pragmatics - all have counter instances.
Another thing folk miss is the difference between a list of things that are true and an explanation of truth, between what is true and what being "true" is. I think you and I do understand what it is for a sentence to be true. So I don't think a definition of truth is needed. I think were we differ is in which sentences we think are true. Some sentences you think are true, other folk think are false.
And this is why we need to clearly differentiate between a sentence's being true and its being
believed true.
And keep in mind that you do know at least some things, and further that you need not rely on things to be beyond doubt before you believe them.
Philosophical thinking can attract folk to extreme views.
Some old notes...
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Statements are combinations of nouns and verbs and such like; Some statements are either true or false, and we can call these propositions. So, "The present king of France is bald" is a statement, but not a proposition.
Beliefs range over propositions.
(Arguably, they might be made to range over statements: Fred believes the present king of France is bald. Some rendition of the possible worlds definition of a proposition is needed.)
“Jeff believes in democracy” looks like a counter example to beliefs ranging over propositions, but the superficial structure hides the proposition: “Jeff believes governments ought be democratic” or some such
Beliefs are stated as a relation between an agent and a proposition. This superficial structure serves to show that a belief is always both about a proposition and about some agent. It might be misleading as the proposition is not the object of the belief but constitutes the belief.
This relation is such that if the agent acts in some way then there is a belief and a desire that together are sufficient to explain the agent's action. Banno wants water; he believes he can pour a glass from the tap; so he goes to the tap to pour a glass of water.
The logical problem here, the philosophical interesting side issue, is that beliefs overdetermine our actions. There are other beliefs and desires that could explain my going to the tap.
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We know some statement when at the least we believe it, it fits in with our other beliefs, and when it is true.
The "fits in with other beliefs" is a first approximation for a justification. Something stronger is needed, but material implication will not do.
It does not make sense to ask if we know X to be true; that's exactly the same as asking if we know X. The "we only know it if it is true" bit is only there because we can't know things that are false.
If you cannot provide a justification, that is, if you cannot provide other beliefs with which a given statement coheres, then you cannot be said to know it.
A belief that is not subject to doubt is a certainty.
Without a difference between belief and truth, we can't be wrong; if we can't be wrong, we can't fix our mistakes; without being able to fix our mistakes, we can't make things better.