Tillich (from The Courage to Be):

The whole [Enlightenment] period believed in the principle of “harmony” — harmony being the law of the universe according to which the activities of the individual, however individualistically conceived and performed, lead “behind the back” of the single actor to a harmonious whole, to a truth in which at least a large majority can agree, to a good in which more and more people can participate, to a conformity which is based on the free activity of every individual. The individual can be free without destroying the group. The functioning of economic liberalism seemed to confirm this view: the laws of the market produce, behind the backs of the competitors in the market, the greatest possible amount of goods for everybody. The functioning of liberal democracy showed that the freedom of the individual to decide politically does not necessarily destroy political conformity. Scientific progress showed that individual research and the freedom for individual scientific convictions do not prevent a large measure of scientific agreement. Education showed that emphasis on the free development of the individual child does not reduce the chances of his becoming an active member of a conformist society. And the history of Protestantism confirmed the belief of the Reformers that the free encounter of everybody with the Bible can create an ecclesiastical conformity in spite of individual and even denominational differences. Therefore it was by no means absurd when Leibnitz formulated the law of preestablished harmony by teaching that the monads of which all things consist, although they have no doors and windows that open toward each other, participate in the same world which is present in each of them, whether it be dimly or clearly perceived. The problem of individualization and participation seemed to be solved philosophically as well as practically.

It is the belief in a preexisting harmony that separates the classical Enlightenment view from a Postenlightenment view. I believe in disharmonious reasons, which is another way of saying that I believe in Pluralism. To extend the music analogy, reason does not produce chords, it produces a chromatic scale, from which harmonies can be made, but only if sour reasonable notes are muted, at least until the melody progresses and the key changes, making the formerly sour note sweet. A harmonious truth must be designed, and design always means making good tradeoffs.