"The only way to progress is by stumbling, falling, and getting up, time and again. Error will always be there because the best decisions are always, to some extent, bound up in error. In the great challenge of separating truth from lies—a goal, perhaps the most human of all goals, that is perfectly possible to achieve—it is essential to bear in mind that in this task there can never be definitive achievements that cannot be challenged later, and no knowledge that cannot be revised. In the great forest of misperceptions and deceptions, mistakes and mirages, through which we roam, the only way that truth can clear a path is by rational and systematic criticism of what is—or passes for—knowledge. Without this privileged expression of freedom, the right to criticize, we are condemned to oppression, brutality, and also obscurantism."