We have to live today by what truth we can get today and be ready tomorrow to call it falsehood.

You cannot wait for certainty before acting, and you also cannot afford to treat your current best understanding as final. Both halves are required. Acting on provisional knowledge is how anything gets done; holding it loosely is how you avoid defending a position years after the evidence turned. Most people manage one of these and not the other, becoming either paralysed or entrenched.

Say what you currently think and what would change your mind, in the same breath. That second part costs almost nothing when you say it early and becomes almost impossible once you have staked your reputation on being right.