Niclas Berggren of Sweden’s Ratio Institute emailed me a quote that would have been fantastic for my book:

When there are rational grounds for an opinion, people are content to set them forth and wait for them to operate. In such cases, people do not hold their opinions with passion; they hold them calmly, and set forth their reasons quietly. The opinions that are held with passion are always those for which no good ground exists; indeed the passion is the measure of the holder’s lack of rational conviction. Opinions in politics and religion are almost always held passionately.

–Bertrand Russell, On the Value of Scepticism

Too bad it’s too late to include it…