Prometheus 6

From: Seeing Reason: Image and Language in Learning to Think
by Keith Stenning
page 73

Logic makes a radical distinction between discovery of a logical or mathematical proof and justification. Logic provides a mechanical criterion of justification. A conclusion is logically justified if it appears in a sequence of steps of derivation all of which follow from the problem statement or earlier derivations from it by one or other of the rules of inference. Each rule application is 'small' enough that it can be checked mechanically. But how we are to find such a chain of rule applications is a matter of discovery. Discovery can be (and historically has been) by dream, hallucination or revelation. Logic does have something to say about discovery, but by far its most intense focus is on the apparatus of justification, and on the very concept of justification itself.