If you would be a real seeker after truth,
it is necessary that at least once in your life
you doubt, as far as possible, all things.
-- Rene Descartes
(1596-1650) French philosopher
Source: Principles of Philosophy, 1644
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[When] Men are not allowed to think freely
about chemistry and biology,
why should they be allowed to think freely
about political philosophy?
-- Auguste Comte.
Isidore Marie Auguste François Xavier Comte(1798-1857)
French philosopher, founder of Positivism and Sociology
Source: The Positive Philosophy, 1830-40
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The free-thinking of one age is
the common sense of the next.
-- Matthew Arnold (1822-1887)