I think the concept of truth has always been present even before we came to be. Thus an idea circling one's head can be described as truth even not at first being demonstrable, afterwards being worked on it can be shown. As proof there's the example of Einstein. At first it takes to approach it mentally, afterwards try and fail and at the end to succeed. That we can't see it in the first place and need proof doesn't take away the truth being there in the first place. It only confirms it.
It can be true, but if you can't demonstrate it, then you don't know it's actually true. That's the point. By working at proving it, then you can prove it ;)
My point is, what drives our minds towards working on something isn't totally random. Yes it can't be shown at first but the truth doesn't care about being shown or not, it just is. Indeed we need the proof to enhance our perception because there's the perception what can't be achieved by our senses doesn't exist.