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The Diagnostic and Statistical Manual of Mental Disorders (DSM), the most widely used reference work for psychiatrists, states that “Delusion is a false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person’s culture or subculture (e.g., it is not an article of religious faith).” (p. 765)
The second half neatly negates the first. Think about what it means… it means that the validity or absurdity of a claim has nothing to do with its attachment to reality, but rather the amount of people who support it and the level of organization of these people (that's an ad populum if I ever saw one). Truth has no consistency over time. One is delusional if they think the Earth is flat now, but not a few hundred years ago. It was perfectly solid believing in witches some time ago, but not now for some reason. It is delusional, thinking aliens are spying on you, but it’s perfectly acceptable believing that an invisible force watches over you all day long, occasionally communicating its wishes. Something that is delusional in one culture is normative a few hundred kilometers away, based not on the reasons to back it up, but the simple number of subscribers.
And a lone psychotic, say Hitler or an Inquisitor, are delusional in their belief that some “race” or “religion” is pure and the others ought to die, only until they gain an audience to their psychosis or only if they don’t have an ancient “sacred” scripture to back them up.
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Which brings us to another widely held, cherished in fact, delusion:
“People should be free to believe whatever they want”
It is widely considered civilized of us to have reached to this conclusion. Accepting each other’s beliefs is considered liberal, fair, and humane. The only qualification offered is “provided we don’t hurt others”.
But let’s dissect this claim.
Firstly, what constitutes “hurt”?
Let’s take astrology, for example. It appears that you’re not hurting others by believing the position of the stars on the sky on the day you were born tells you all you need to know about your future. One who really believes in it might make terrible mistakes, financial, personal etc, because “their signs told them it was a great idea”, thus hurting themselves. But say they don’t even believe “so much”. Say their belief in astrology is limited to the personality traits of each sign. Each time these people ask your sign, they think they know everything about you. You’re labeled in their minds as “committed Taurus”, “ambitious Capricorn”, “hypocrite Gemini” or whatever. Though they don’t hurt you exactly, they do lessen your interaction. They are unfair to you by not bothering to see who you really are. They miss out and you miss out on a real human connection for the sake of simplicity, emotional safety and intellectual laziness.
Secondly, what is “freedom” concerning beliefs?
Are we free to believe that rocks are alive? Are we free to believe that plastic is good for the environment? Are we free to believe that oranges are bad for our kidneys? Are we free to believe that pouring coffee all over the keyboard makes it work better? Are we free to believe that wool must be washed in boiling water? Are we free to believe that we dance the rain to us?
Again, not all of these claims cause harm, but all of them pose a potential direct or indirect threat to us, others or the environment, through the misrepresentation of reality inside our brains. There is no reality-opposing belief that really, truly doesn’t harm anyone, even if only the person who has it or their children who are raised indoctrinated by it. The distance between their reality and the reality of the Universe will inevitably lead in the very least to someone’s disappointment and confusion.
So, are we “free” to believe whatever we want? Should we be “free” to believe whatever we want? Should we want to be “free” to believe whatever we want?
The answer is no. We are free to use our imagination and entertain all sorts of ideas, but in the end we are and should be constantly restrained by reality, by facts, by evidence, by critical thinking.
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But, in the end, it comes down to reality for the sake of reality. Just the fact that we need to argue about why it’s a good idea for our beliefs to be aligned with (scientific) reality proves how much we have surrendered ourselves to "supernatural" claims.