Eratosthenes's only tools were sticks, eyes, feet, and brains; plus a zest for experiment. With those tools he correctly deduced the circumference of the Earth, to high precision, with an error of only a few percent. That's pretty good figuring for 2200 years ago.
Those wretches who never have experienced the sweets of wisdom and virtue, but spend all their time in revels and debauches, sink downward day after day, and make their whole life one continued series of errors.
There is no more evil thing in this world than race prejudice, none at all. [...] It justifies and holds together more baseness, cruelty, and abomination than any other sort of error in the world.
Not complete inaction, which is an error, a confusion, a self-delusion, an impossibility, but action full and
free done without subjection to sense and passion, desireless and unattached works, are the first secret of perfection.
To free a man from error is to give, not to take away. Knowledge that a thing is false is a truth. Error always does harm; sooner or later it will bring mischief to the man who harbors it.
What is toleration? It is the prerogative of humanity. We are all steeped in weaknesses and errors: Let us forgive one another's follies, it is the first law of nature.