Much of what we know is called “common sense.” Either we have learned its precepts and perspective from others, or we have asked questions and come up with answers that are usually satisfactory. Proverbs are examples of common sense codified in easily-remembered phrases: “a stitch in time saves nine”, “early to bed, early to rise, makes one healthy, wealthy and wise”, “red sky at night, sailor’s delight; red sky at morning, sailor take warning”, and so on. The trouble is, proverbs often contradict one another. “Lightning never strikes the same place twice” is (usually!) true, but the French say, “never two without three” (jamais deux sans trois). Good as far as they go.
Common sense that we learn ourselves requires observation, raising and answering questions about specific situations. It is usually acquired by experience: we compare and contrast to previous similar occasions. Such learnings are vital to survival, success in relationships, and in work, beyond what proverbs can teach.
In his book The Black Swan, Nasim Nassar Talib describes how it was commonly believed that all swans are white. Until, in Australia, black swans were observed. The term “black swan” has moved into ordinary speech to denote something surprisingly unknown. He also tells a parable about the turkey who is happy to be fed by the nice farmer every day. Until the day he comes not with food, but with an axe…
Just a theory?
So there are limits of common sense, which can also be non-sense, as it is always descriptive, not explanatory. When someone comes up with an explanation of a phenomenon, common sense often resists it. Moving from the everyday world to the realm of theory is difficult, and the results are often hard to grasp in our everyday experience. For instance, this book is being written on a computer, which depends upon quantum physics to work (“tunneling electrons”). The fundamental explanation of how subatomic particles like electrons behave is that they can be a wave or a particle, depending on how you look at them. In the everyday world, that is ridiculous, but the fact that my computer works is proof that it is true. And this holds for your computers, tablets, smartphones, etc., as well.
But even a field like say, abstract topology requires that its practitioners have enough common sense to find their way to the office.
More on theory
Here is a fact: Louis XVI, King of France, died at the age of 38 on Monday, January 21, 1793, in the Place de la Concorde in Paris on a decapitation machine called a guillotine operated by a man named Sanson. This is indisputable — it happened. Why it happened remains a subject for inquiry, in other words, we can continue to add more meaning to this event.
That requires developing and using theory. And theories are what has been proven to explain the facts at hand. Until new facts or a new perspective call a theory into question. Theories can and even should be overturned. “Is that your final answer?” a popular television host asks his victims, er, contestants, on a quiz show. Well, no. There is no completely “final answer” to anything, at least not in the universe we dwell in.
You may recall the Greek myth of the chariot of the Sun-god, Helios. The story “explained” how the Sun rises in the east and sets in the west: it is a flaming chariot with a god holding the reins, making a daily run. Helios, like most of the gods, had a dalliance with a human woman, Clymene, which produced a son, Phaethon. The lad went to meet his divine father in order to assert his claim to be Helios’ son. In their meeting, he got Helios to agree to any favor at all (always dangerous to agree to!). The boy demanded to take the chariot across the sky. Of course, he was not capable, and he let the chariot burn parts of the Earth. This led the chief god, Zeus, to kill him with a thunderbolt.
To paraphrase G. K. Chesterton, the path of the collective human intellect lurches wildly across time like the Sun in Phaethon’s hands across the sky, burning out old formulations of truth and flinging forth new and more comprehensive ones.
Once the ancient Greeks began to throw off such myths as fanciful and to ask questions of what they actually experienced, that wild adventure began in earnest. Nevertheless, it took two thousand years after Aristotle for the Polish astronomer Copernicus to establish firmly that the Sun, Moon and planets do not revolve around the Earth (though it had first been proposed as early as the 3rd century B.C. by Aristarchus of Samos). It was not until the 1920s that Edwin Hubble showed that there is more than one galaxy in the Universe, building on discoveries by Henrietta Leavitt. As for the Earth’s rotation on its axis, while many had speculated since Antiquity that the sun’s apparent motion was due to the planet’s rotation, it was only until 1851 that Léon Foucault’s pendulum actually demonstrated it.
So across centuries, people used their senses to observe phenomena, which were complemented by mathematics, and then by technology (the telescope), then other techniques to gather data, seek insights, formulate questions, and make judgments. With each advance, everything changes: more information more accurately measured, better interpretations, leading to more refined questions, and better ways of verifying the truth of what is under study.
This is a never-ending process, which also involves history and debate, as well as establishing theories and communicating what has happened. And it fights bias at every step, as well as inattention, stupidity, and mistaken or lazy judgments.
Knowing the truth is hard work. But it is better than the alternative. How much is freedom worth to you?
[This story, along with “Just what is meaning?”, “Just what is truth?”, “Just what is language?”, and “Just the facts, Ms. AI”, are excerpts from my unpublished book, Set You Free: Know Your Own Mind. Write me for more information…]
 The Black Swan: The Impact of the Highly Improbable, (New York: Random House, 2007).
 See e.g., https://spectrum.ieee.org/semiconductors/devices/the-tunneling-transistor Accessed January 22, 2018.
 Orthodoxy (London: Simon & Brown, 2011)