From Johann Gottfried Herder's "Letters for the Advancement of Humanity (1793-7)"
Free investigation of the truth from all sides is the sole antidote against delusion and error of whatever sort they may be. Let the deluded person defend his delusion, the person who thinks differently his thought; that is their business. Even if both of them fail to be corrected, for the unbiased person there certainly arises out of every criticized error a new reason, a new view of the truth. Let it only not be believed that truth can ever be captured, or even kept fast in jail for eternity, by means of armed delusion! Truth is a spirit and communicates itself to spirits almost without a body. Often its sound may be stirred at a single end of the world, and it resounds in remote lands; but the river current of human cognition always purifies itself through oppositions, through strong contrasts. Here it breaks off, there it starts; and in the end a long- and much-purified delusion is regarded by human beings as truth.
I have a problem understanding this text with regards to the notion of truth. If we say man is free to think at his own will then why is there a threat of armed delusion? Furthermore, I seem to understand that the ultimate truth essentially evolved through opposition governed by communications and then in the long run its said that the supreme truth is finally a much-purified delusion, why is it that the truth is still regarded as a delusion?