Our understanding of truth comes from Plato, who taught that truth was perfect, unchanging and absolute, unlike the world of everyday experience. Truth could not be seen directly, so therefore it could only be discovered by making our thinking perfect; the more perfect our thinking, the closer it would be to truth.
Plato expressed his ideas in the form of dialogues, conducted through the character of his older friend Socrates. Socrates asserted that he himself knew nothing, and so he treated all ideas with equal indifference. He took the view that if he could find fault with an idea, it was not perfect and therefore it could not be true.
Platonic truth was then adopted by the Church through Saint Augustine. Whereas Platonic truth existed in a world of pure ideas, for Augustine, truth existed in the Gospels. His view was that the Church owned the Gospels, and so therefore it owned truth. It followed that any idea not in conformity with Church dogma was untrue and had to be attacked as a heresy. The persecution of the heretics followed as a direct result.
Gospel truth lasted as long as the Renaissance, when one of the fundamental dogmas of the Church, that the earth was at the centre of creation, was successfully challenged by Copernicus. After this came the secular Enlightenment. The Encyclopedie was created to replace the Gospels as the source of truth. So now the Church no longer owned truth and instead secular science owned it; but there was still only one truth.
Because there is no Pope of science, truth is now what is agreed by the majority. This is ‘paradigm’ truth. So we have gone from Platonic truth to Gospel truth to Paradigm truth. We still regard truth in the way Plato did, that it is perfect, pure and unchanging, but now it is the truth of majority opinion. Our conception of truth has changed considerably since the time of Plato, but we still treat it as though it is the same truth.