Eratosthenes was the director of the great library of Alexandria, the Centre of science and learning in the ancient world. Aristotle had argued that humanity was divided into Greeks and everybody else, whom he called barbarians and that the Greeks should keep themselves racially pure. He thought it was fitting for the Greeks to enslave other peoples. But Erathosthenes criticized Aristotle for his blind chauvinism, he believed there was good and bad in every nation.

The suppression of uncomfortable ideas may be common in religion or in politics, but it is not the path to knowledge, and there's no place for it in the endeavor of science. We do not know beforehand where fundamental insights will arise from about our mysterious and lovely solar system. The history of our study of our solar system shows us clearly that accepted and conventional ideas are often wrong, and that fundamental insights can arise from the most unexpected sources.

We wish to find the truth, no matter where it lies. But to find the truth we need imagination and skepticism both. We will not be afraid to speculate, but we will be careful to distinguish speculation from fact.

Religions are tough. Either they make no contentions which are subject to disproof or they quickly redesign doctrine after disproof. ... near the core of the religious experience is something remarkably resistant to rational inquiry.

Since World War II, Japan has spawned enormous numbers of new religions featuring the supernatural.... In Thailand, diseases are treated with pills manufactured from pulverized sacred Scripture. Witches are today being burned in South Africa.... The worldwide TM [Transcendental Meditation] organization has an estimated valuation of $3 billion. For a fee, they promise to make you invisible, to enable you to fly.

When permitted to listen to alternative opinions and engage in substantive debate, people have been known to change their minds. It can happen.

In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion.