The first part of this question is an age-old one that has been around since long before Pontius Pilate asked it of Jesus at His pre-Crucifixion “Trial”. And the answer to the second part of our question depends on what type of truth we’re talking about. So let’s start with some definitions:

There are two kinds of truth:

Subjective truths (such as “that’s a pretty dress” ; or, “we should save spotted owls”)

and

Objective truths (“that’s a new dress” ; or, “humans rights are more important”)

Subjective truths are determinable by the individual -- even changeable. One day, you think the dress looks pretty on you ; the next day you don’t. Objective truths, on the other hand, remain unchanged, no matter how much we deny them. Jesus will always be the Son of God.

As Philip K. Dick put it, “Reality [a.k.a, truth] is that which, [even] when you stop believing in it, doesn't go away.” https://www.google.com/search?q=%E2%80%9CTruth + is + that + which + continues + to + exist%2C + even + if + you + stop + believing + in + it.%E2%80%9D&rlz=1C1CHBF_enUS906US906&oq=%E2%80%9CTruth + is + that + which + continues + to + exist%2C + even + if + you + stop + believing + in + it.%E2%80%9D&aqs=chrome..69i57.983j0j7&sourceid=chrome&ie=UTF-8

Yet we humans have a long, disastrous history of trying to write our own version of objective truth. Examples include idolatry, atheism, the Protestant Rebellion, Nazism, humanism, evolutionism, and Communism in all its versions (socialism, Marxism, and the like).

And just why do our attempts to rewrite truth have such horrific results? Well, for 2 basic reasons:

First of all, because they fly in the face of God, and thus invite the Devil in ;

And secondly, because they fly in the face of the reality -- like trying to force a square peg into a round hole: it simply doesn’t work. And the more we try and force it to work, the worse the results get.

And yet we humans keep banging our heads up against the “I’ll-define-my-own-reality” wall until we black out. Trying to construct our own objective truths, apart from reality, is like being in a never-ending haggling war with a used-car salesman. It gets you nowhere, and still the empty car sits there, waiting to be driven. Objective truth is objective truth -- no matter whether we agree with it or not.

Please know this: It is extremely harmful to the human person to live according to false truths. Yet it is extremely beneficial to the human person to live in accordance with real objective truths.