Follow the Scientific Method to find the truth.
I see truth as when the Scientific Method triumphs.
By that, I mean as long as a scientist follows the Scientific Method they will find the truth. This might mean they have to abandon false theories they have based their lives-work on- which many can’t. But that is science. Sometimes a scientist life’s work is false because it doesn’t live up to the Scientific Method. In that case, the scientist needs to loose the ego and develop a new theory. Unfortunately, many can’t.