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 History shows that knowledge grew when speculation was perfectly free in Greece, and that in modern times, since restrictions on inquiry have been entirely removed, it has advanced with a velocity which would seem diabolical to the slaves of the mediæval Church. Then, it is obvious that in order to readjust social customs, institutions, and methods to new needs and circumstances, there must be unlimited freedom of canvassing and criticizing them, of expressing the most unpopular opinions, no matter how offensive to prevailing sentiment they may be. If the history of civilization has any lesson to teach it is this: there is one supreme condition of mental and moral progress which it is completely within the power of man himself to secure, and that is perfect liberty of thought and discussion. The establishment of this liberty may be considered the most valuable achievement of modern civilization, and as a condition of social progress it should be deemed fundamental. The considerations of permanent utility on which it rests must outweigh any calculations of present advantage which from time to time might be thought to demand its violation.

It is evident that this whole argument depends on the assumption that the progress of the race, its intellectual and moral