Can you explain why some people believe there is no such thing as absolute truth? How would you explain this concept to someone who believes otherwise?

I am convinced there is no such thing as ‘absolute (inductive) truth’ - we only have deductive truths in that sense.

Correspondence truth

“Truth” = mapping function between a set of linguistic propositions and some value assignment, often “true” or “false.”

You have laws of logic: identity, excluded middle, but they function on non-contradiction and are linguistic representations of abstractions on sensory experience. Try and make a true or false statement, or engage in any form of “proof” finding without assuming them - it can’t be done. There’s your absolute truth, humans. That’s it.

And that’s the limit of it. Literally every other claim or objective observation must be an inductively soft falloff toward complete and irreconcilable ignorance (epistemic nihilism of a sort).

We are hideously ignorant in almost all practical senses of the word. Helplessly.