P1: That was my fault, I didn&#x27;t state that clearly.  I should have said &quot;The valid principles of induction define that line...&quot;  We have the principles of deduction that tell us when something is false but we are missing the principles of induction that tell use when something is true (in a given context). This is a general need so it spans all theories in all fields; how do we know and are certain the sun will rise, evolution is true, there ARE atoms, etc. There must be a criteria by which to say, in the current context of knowledge we know enough to say something is <i>true</i> and certain.<p>P2: You anticipated my answer, Kant&#x2F;Popper is an end-run evading the issue, i.e., we can only prove thing false never true and certain. The truth is unattainable. I think it is a valid question and needs to be solved. But to solve it we need a full, valid epistemology explaining how reason works <i>in toto</i> to achieve <i>certain</i> knowledge.<p>I think this is the same problem as in physics and all the contradictions and paradoxes in QM and GR. Physics is hung up on all sorts of confusing issues that seem to revolve around the nature of the observer and time.  This makes sense to me because deduction is based on a metaphysical fact that contradictions do not exist which we (try) to abide. But this is half the story, what is missing is an epistemological principle that tells us what our brains do to create true knowledge. Whoever solves this problem will revolutionize physics and allow us to create AI (in my judgement).