As much as we owe to 18th-century thinkers, we should not forget that they were indebted to intellectual traditions that valorized the pursuit of truth and, ultimately, agreement. Truth, however, is not the standard of liberal democracies, which function not by imposing a few grand ideas handed down from on high, but by encouraging a marketplace of diverse, competing, unrestrained opinions -- as portrayed in the Maulbertsch painting. Lest we forget it, the pursuit of truth in the past also involved the assiduous refutation of error. It has been trial and error, however, not dogma, in whatever form, that created the West. Freedom of speech, if we are serious about it, must also allow for unpopular, even "wrong," opinions.
Picture credit: Städtische Kunstsammlungen Augsburg