7. The sources of certainty
1. Definition and types of evidence
Evidence is an obvious certainty, expressed in such perceptible way that nobody can reasonably doubt about it. Evidence is the rule of truth and the right cause of certainty. For example, the whole is bigger than a part, the man lives, the water wets, the gold is solid.
Very clear truths without discussion are evident. We can differentiate four types of evidences: immediate, mediated, intrinsic and extrinsic.
a) Immediate evidence. When truth shows itself directly. Logical principles of identity, contradiction and excluded middle are examples of immediate evidence. The mathematics axioms are evident in a straight and immediate way.
b) Mediated evidence. It is the evidence that cannot be seen directly but after reasoning from other truths. You achieve it after a series of deductions.
c) Intrinsic evidence. You can achieve intrinsic evidence when you start from truths offered to our reason as true ones. The immediate and the mediated evidences in Mathematics are intrinsic.
d) Extrinsic evidence. It is the evidence justified in someone’s authority. For instance, we cannot see immediately historical events, but we believe in them due to the fact that historian have deeply studied the facts and have human authority so that we believe it. Church has the full divine authority and we believe in what she tells us as true.