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 suppressed freedom and imposed upon man a weary struggle to recover the freedom which he had lost. Is it not conceivable that something of the same kind may occur again? that some new force, emerging from the unknown, may surprise the world and cause a similar set-back?

The possibility cannot be denied, but there are some considerations which render it improbable (apart from a catastrophe sweeping away European culture). There are certain radical differences between the intellectual situation now and in antiquity. The facts known to the Greeks about the nature of the physical universe were few. Much that was taught was not proved. Compare what they knew and what we know about astronomy and geography—to take the two branches in which (besides mathematics) they made most progress. When there were so few demonstrated facts to work upon, there was the widest room for speculation. Now to suppress a number of rival theories in favour of one is a very different thing from suppressing whole systems of established facts. If one school of astronomers holds that the earth goes round the sun, another that the sun goes round the earth, but neither is able to demonstrate its proposition, it is easy for an authority, which has coercive power,