English mathematician and philosopher, W. K. Clifford.

Via Keith Burgess-Jackson comes this passage from William Kingdon Clifford’s “The Ethics of Belief”:

To sum up: it is wrong always, everywhere, and for any one, to believe anything upon insufficient evidence.

If a man, holding a belief which he was taught in childhood or persuaded of afterwards, keeps down and pushes away any doubts which arise about it in his mind, purposely avoids the reading of books and the company of men that call in question or discuss it, and regards as impious those questions which cannot easily be asked without disturbing it; the life of that man is one long sin against mankind.

If this judgment seems harsh when applied to those simple souls who have never known better, who have been brought up from the cradle with a horror of doubt, and taught that their eternal welfare depends on what they believe; then it leads to the very serious question, Who hath made Israel to sin?

It may be permitted me to fortify this judgment with the sentence of Milton—

“A man may be a heretic in the truth; and if he believe things only because his pastor says so, or the assembly so determine, without knowing other reason, though his belief be true, yet the very truth he holds becomes his heresy.”

And with this famous aphorism of Coleridge—

“He who begins by loving Christianity better than Truth, will proceed by loving his own sect or Church better than Christianity, and end in loving himself better than all.”

Inquiry into the evidence of a doctrine is not to be made once for all, and then taken as finally settled. It is never lawful to stifle a doubt; for either it can be honestly answered by means of the inquiry already made, or else it proves that the inquiry was not complete.

“But,” says one, “I am a busy man; I have no time for the long course of study which would be necessary to make me in any degree a competent judge of certain questions, or even able to understand the nature of the arguments.” Then he should have no time to believe.

Wow. Pretty strong words.

As a critical thinking evangelist, I am of course attracted to Clifford’s assertion that it is immoral to form opinions and beliefs based on insufficient evidence, to avoid any evidence and arguments that might contradict our opinions, and to stifle any doubts we may have. Really he’s asserting that it is immoral to not engage in critical thinking.

But as a critical thinker, I am forced to hold my own attraction to this claim at arm’s length, and examine this assertion fairly and objectively based on the evidence. (Ha. See what I did there?)

There are certainly countless cases where serious negative consequences have occurred because people have failed to engage in critical thinking. For example, the subprime mortgage crisis was caused by critical thinking gaffs on the part of policy makers, lenders, and borrowers. I also happen to think the war in Iraq was prompted by beliefs that were unfounded, and I am of the opinion that the current Democratic-led push for health insurance reform is grounded on flawed thinking. I would also point the reader to the web site What’s The Harm? (in my blogroll), which documents real-world cases where people have been harmed or injured due to a lack of critical thinking.

And don’t forget this:

Jenny McCarthy Body Count

So, it’s almost axiomatic in my mind that a lack of critical thinking produces extremely harmful results.

But. I can’t help but think it’s not necessarily immoral. For example, I suspect that George W. Bush really believed the intelligence reports about weapons of mass destruction in Iraq. Turns out he was wrong to do so. Does that make him immoral, or merely human? If he really believed it — even though mistakenly, possibly fueled by wishful thinking and the confirmation bias — then he also believed it was his moral duty to do something about it.

The human condition is this: we are imperfect. We suffer from huge cognitive biases and logical fallacies, that are hardwired into our brains. Critical thinking is a constant uphill fight to overcome these. And most people have no real education or training in critical thinking; in fact, most probably aren’t even aware of what critical thinking is. Even some of our very best critical thinkers — Albert Einstein and Isaac Asimov, for example — have had bouts of poor critical thinking at times. (As discussed in this book, for example.)

So sadly, I’m afraid Clifford’s assertion may be going too far.

Or am I just being too forgiving?