Conservatism: the philosophical position that one should oppose new ideas and practices.
Moderatism: the idea that one’s pursuit of truth should never conflict with the majority opinion — too much.
Extremism: the belief that one should adopt beliefs opposed to the majority.
In relation to reality, in any given society, conservatives, moderates and extremists have similar ideas, since they have no epistemological method by which to come to believe anything else.
Radicalism: the idea that one should reach conclusions based solely on the evidence without regard for other people’s opinion. In other words, radicalism is intellectual honesty consistently followed to ultimate conclusions. Most people who have made a difference in history have been radicals.
True radicals tend to be opposed by conservatives, moderates, and extremists, since they are the farthest removed from the consensus.
I don’t know of a single perfectly consistent radical, either personally or in history. Everyone whom I have known or studied has compromised when the facts became too uncomfortable or inconvenient. It is not a matter of intelligence. To be absolutely honest with oneself and interested in the truth is the hardest thing there is.
What are the facts? Again and again and again — what are the facts? Shun wishful thinking, ignore divine revelation, forget what “the stars foretell,” avoid opinion, care not what the neighbors think, never mind the unguessable “verdict of history” — what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!
— Robert A. Heinlein