A question for those who believe truth is not absolute

[Aegon]

I got into an argument with a friend about this a little while ago.

He was saying that all truth is subjective, so if you believe something that makes it true to you. But I disagreed. I think that there is an absolute truth and if you sway from it, you're wrong. It's false. You thinking it's true doesn't magically make it so. Something being true to you while not actually being true just means you're wrong. And saying it despite believing it doesn't make you right. You're lying. Maybe not intentionally, but you are.

And even if you argue that no truths can be absolute for all these reasons mentioned, there are truths that are as absolute as they can be. Saying "well nothing is objective man" misses the point. It doesn't matter, you're still wrong.

  Ok good, now explain how can you know what that objective truth is, if all you can know is the truth of your own personal experience?
You cant speak for anyone elses truth now can you?

See, this is where you lose me. Nobody looks at a banana and sees a fucking cube, right? Bananas aren't shaped like cubes. If someone saw a cube-shaped banana you'd need to get your head checked. Absolute truth that bananas are not cube shaped. No?