Why we should not outrightly dismiss repugnant ideas

Consider the Ptolemaic system, otherwise known as the geocentric model. According to this system, the Earth is at the center of the universe, and the heavenly bodies in the sky, such as the Sun and the planets, revolve around it.

Geocentrism is a simple idea in theory. Indeed, to us here on planet Earth, it feels as though our planet is unmoving, and our day-to-day language still reflects such an attitude, such as when we say that the Sun rises in the east and sets in the west. (The Sun doesn't rise or set; the Earth rotates.) However, in practice geocentrism must deal with the reality that the planets don't appear to move in simple, smooth orbits around the Earth. For example, Venus and Mercury appear (from Earth) to move backward at times. How could this be so if they orbit around the Earth?

Ptolemy, who lived in the 2nd century, is credited with a solution that explains such odd phenomena, like backwards-moving planets. According to his system, the planets do not follow simple, smooth orbits but instead follow a sort of double orbit whereby each planet revolves through an orbital path, called a deferent, whose center itself revolves around the Earth along yet another orbit, called an epicycle. It's an orbit following an orbit. The end result is a convoluted, overly complex system that actually did a pretty good job of predicting the motions of the heavenly bodies for about 1,500 years, up until the system was replaced with the Copernican system, also known as heliocentrism. What heliocentrism says is that the planets indeed do follow simple, smooth orbits; only, the planets orbit around the Sun, not the Earth. The end result of the this system is an elegant, simple system that has even more predictive power than the more complex one that it replaced. The replacement of the Ptolemaic system with the Copernican system marks one of the great triumphs of Occam's Razor.

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Much of human thought and behavior is constrained by the avoidance of repugnant ideas. Repugnant ideas are those that suggest inescapably insulting or deplorable facts about the universe. Here are some examples of repugnant ideas:

• The universe is unfair.
• Life is meaningless.
• The future will be no better than the past.

The list could go on. The common theme here is that these are ideas that present (or result from) a world view that is just kinda depressing and sad. In the case of these three repugnant ideas, what makes them even sadder is that there doesn't appear to be enough objective evidence to suggest that they're false, though most people do reject them as false. Karma, God, and American Exceptionalism are each examples of ways that people justify a rejection of these repugnant ideas. Call these justifications comfortable ideas.

And yet karma, God, American Exceptionalism, as well as most other comfortable ideas, each fall prey to same sort of convoluted, overly complex modeling as does the Ptolemaic system. Each requires that we assume the truth of something that cannot be directly observed, and often, as is the case with these three repugnant ideas and their resulting comfortable ideas, the extra complexity does not increase predictive power but likely hinders it. Each comfortable idea necessarily leads to its own equivalent of deferents and epicycles. In the case of astronomical modeling, predictive power was increased by rejecting the comfortable idea that the Earth is at the center of the universe and embracing the repugnant idea that the Earth is just yet another planet revolving around the Sun. With respect to the three repugnant ideas listed above, we might increase our understanding of why bad things happen to good people, why life doesn't offer a clean beginning and end to every life, and why poverty and war never go away despite all kinds of miraculous technological and scientific advances—if only we allow for the possibility that the universe has some depressing fundamental truths going on with it.

The path to wisdom is the ability to see things different ways, and the way to see things different ways requires that we accept the possibility that things are not what we want them to be. This requires a grown-up disposition from us. It may be that the universe is indeed fair, life is indeed purposeful, and things are indeed getting better all the time. But getting hung up on any of these points severely limits our ability, as individuals and as a society, to frame problems in the way that is most practical and makes most sense. We should not outrightly dismiss repugnant ideas.