The rationalist/empiricist debate is a philosophical one.
As is truth.
What do you mean by that?
There are some things which cannot be determined absolutely, they are subjective:
"Trump is a bad president", "The Spice Girls are the greatest musical act of all time"
These are highly subjective statements, they may be interesting to discuss but ultimately there is no "absolute" truth about them.
Then there are things like "Brexit is the wrong decision for the UK".
Now, that is a complex topic which has been discussed ad nauseum over here. One aspect of it is the economy - some thing the sky will fall in economically if we leave, some think we'll be just fine. Let's say in 10 years time when we've left the economy is doing fine. People who wanted to leave will say "we told you so!". Or let's say the economy has done poorly, people who wanted to stay will say "we told you so!". The problem with those arguments is we don't know how the economy would have done had the other decision been made. In scientific lingo there is no "control". So while there might be an absolute truth about this, it is pretty much impossible to determine.
But with something like, say, the shape of the earth, there is a clear, absolute truth about that. Let's simplify things and say it's either flat or a globe...well, it can't be both. If you think it's flat and I think it's a globe then one of us is wrong. And while you can always claim there is some doubt the objections get increasingly desperate and spurious when, say, you're shown a load of photographs which clearly demonstrate horizon dip. So while yes, there is technically always some doubt about anything (outside of the fairly limited language of mathematics), the doubt about some things becomes increasingly theoretical and it's a weird way to live your life. You'd never get out of bed in the morning without checking to make sure the floor had not disappeared overnight or replaced by a replica which is brittle and you'd fall right through. No-one really lives their life doubting everything like that.