Well, I think that when we ask what "truth" is, everyone has their own idea of the what realm this question is being applied. So it makes the answers vary.

I think that much of us can agree on many things about truth, but not in every realm. For example, many groups of people have their own idea of what is true regarding the origins of life. But that's mainly because we weren't there when it happened. So obviously, it's a hotly debated topic.

For the most part, it's difficult to determine truth about those things which can't be measured or observed. People can lie to us, but we can't observe what's actually in their hearts. Sometimes, even their actions can be deceptive.

Interpreting ancient documents can sometimes be tricky, which explains the study of Hermeneutics, something many people aren't even aware exists. Of course, it's not always a 100% exact study, just like science; but it can give a solid idea of what's probably true regarding interpretation of ancient documents.

Sometimes, it may even be easier to prove a falsehood than it is to prove a truth. If that makes any sense at all.