Ours is an age of criticism, to which everything must be subjected. The sacredness of religion, and the authority of legislation, are by many regarded as grounds for exemption from the examination by this tribunal, But, if they are exempted, and cannot lay claim to sincere respect, which reason accords only to that which has stood the test of a free and public examination.
Reason in a creature is a faculty of widening the rules and purposes of the use of all its powers far beyond natural instinct; it acknowledges no limits to its projects. Reason itself does not work instinctively, but requires trial, practice, and instruction in order gradually to progress from one level of insight to another.
This spirit of freedom is expanding even where it must struggle against the external obstacles of governments that misunderstand their own function. Such governments are illuminated by the example that the existence of freedom need not give cause for the least concern regarding public order and harmony in the commonwealth. If only they refrain from inventing artifices to keep themselves in it, men will gradually raise themselves from barbarism.
Enlightenment is man's emergence from his self-imposed immaturity...No thing is required for this enlightenment.. .except freedom; and the freedom in question is the least harmful of all, namely, the freedom to use reason publicly in all matters.
That Logic has advanced in this sure course, even from the earliest times, is apparent from the fact that, since Aristotle, it has been unable to advance a step, and thus to all appearance has reached its completion.