Common Sense Is a Philosophy Too, and It Shaped the Founders' Plain Talk

There is a type of person, and you have met him, who can prove to you in four syllogisms that the chair you are sitting on does not exist. He is not joking. He has a degree. And when the proof is finished he will pull out that same chair and sit down in it, because he is not an idiot, only a philosopher.

That small comedy is the whole subject of this post. For about a century and a half, a school of thinkers insisted on a proposition that most of us find quietly obvious: that the ordinary person knows the real world is there, knows that cruelty is wrong and knows that two and two make four, and does not need a professor's permission to know it. They called their position common sense. It was an actual philosophy, argued by serious men, and it came to America in the baggage of a Scottish minister who taught a future president. It also helps explain why the Declaration of Independence reads the way it does, and why conservatives still trust the judgment of ordinary citizens.

A warning before we begin, since this is a confusing name. The common sense I mean is not Thomas Paine's pamphlet Common Sense, published in January 1776, which argued for independence. Paine's title used the everyday phrase. The Scottish school, which is my subject, made the phrase into a method. They overlap in spirit and they are different things.

The problem Hume left behind

To see why the school mattered, start with the problem. In the seventeenth and eighteenth centuries, philosophers in the line of John Locke and Bishop Berkeley held that what the mind directly knows are its own ideas: impressions, images, sensations. The outside world is something you infer from them. That was a reasonable way to start, and it led somewhere uncomfortable.

David Hume, the Scottish philosopher, followed the logic all the way down. His Treatise of Human Nature (1739 and 1740) argued that if all we ever perceive are our own impressions, then we cannot prove an external world, cannot prove that one event causes another and cannot prove that the self is more than a bundle of perceptions. He pressed the same skepticism in his Enquiry Concerning Human Understanding (1748). His own conclusion was striking. He admitted that when he left his study, his skepticism vanished. He dined, played backgammon, talked with friends and was merry, and when he came back to the argument it seemed cold and strained and ridiculous. Nature, he said in effect, cures what reason cannot.

That honest admission is the opening Thomas Reid walked through. Here was the most acute philosopher of the age conceding that his own theory could not be lived. Reid's response was to ask whether the theory, rather than the living, was what needed repair.

Reid's answer

Thomas Reid (1710 to 1796), a Scottish minister and professor of philosophy at Glasgow, published An Inquiry into the Human Mind on the Principles of Common Sense in 1764 and Essays on the Intellectual Powers of Man in 1785. His argument, in plain words, ran like this.

1. Hume's conclusions are absurd, and an argument that ends in an absurdity has a faulty premise. If a chain of reasoning ends with "you cannot know that there is a world, or that you have a past," then something went wrong at the start.
2. The faulty premise was the "way of ideas." The assumption that the mind knows only its own images, and must build the world out of them, was never proved. It was simply inherited from Descartes and Locke. Reid denied it. In perception, he said, we are directly aware of things, not of pictures of things.
3. Some beliefs are first principles, and they need no proof. We believe that we exist, that the things we perceive exist, that we are the same people we were yesterday, that other minds are real, that some things are right and wrong. These beliefs come with the equipment of a human mind, and every argument, including the skeptic's, leans on them. The skeptic who offers you an argument assumes that you can trust your reason and that the words will keep their meaning from the first line to the last.
4. Therefore they are the proper starting point of philosophy, not its casualties. Reid called them the principles of common sense. They are common because every sane person holds them, and sense because they are the judgments of an intact mind.

Notice the move. Reid did not say that philosophy is useless. He said it must begin where life begins, and that a theory that contradicts what every human being cannot help believing has refuted itself. It is the difference between a map and a territory: when the map says the river is not there, you do not rebuild the river.

Alexander Hamilton stated a close cousin of this idea in Federalist 31. "In disquisitions of every kind," he wrote, "there are certain primary truths, or first principles, upon which all subsequent reasonings must depend." He was talking about politics and geometry, not about Reid, but the structure is identical. Every argument rests on something that is not itself argued.

From Glasgow to Princeton

How did a Scottish school reach American statesmen? Through a man.

John Witherspoon (1723 to 1794) was a Presbyterian minister in Scotland, and in 1768 he crossed the Atlantic to become president of the College of New Jersey, which later became Princeton. He brought with him the Scottish moral philosophy of the day, including the common sense tradition. He taught the senior class a course in moral philosophy, and his Lectures on Moral Philosophy survive. He was also a politician: he served in the Continental Congress and signed the Declaration of Independence in 1776, the only active clergyman to do so.

Among his students was James Madison, who entered the college in 1769 and finished in 1771, completing the course in two years and staying on for study with Witherspoon afterward. Madison would become the principal architect of the Constitution and the principal drafter of the Bill of Rights. I will be careful about the claim. I cannot give you a list of every sentence in the Federalist that came from a Witherspoon lecture, and I will not invent one. The fair statement is that the future "father of the Constitution" was trained by a teacher steeped in Scottish common sense philosophy, in a setting where that style of reasoning was central. How deep the influence ran is a matter historians argue about. That it was available, and that Madison absorbed an education shaped by it, is not.

Witherspoon's own politics lean the same way. He argued that moral truths are accessible to ordinary reason and conscience. In his lectures he held that we have a moral sense, a capacity to perceive right and wrong, and that this sense is shared by human beings generally. That sounds like Reid because it comes from the same school.

Self-evident truths

Now the connection to the document everyone knows. The Declaration of Independence, adopted July 4, 1776, says: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."

Read the word "self-evident" with Reid in mind. A self-evident truth is a first principle: not the conclusion of a proof, but something you see by looking at it clearly. It is precisely the kind of thing that common sense claims to know directly. The Declaration does not argue at length for human equality. It states it as a truth that the reader will recognize. That was the style of the age, and it was the style of a school of philosophy that said such truths are available to anyone with a working mind and a conscience.

I do not want to overclaim. Self-evidence has older roots in the natural-law tradition that stretches from Cicero through Aquinas to Locke, and Jefferson drew on several sources. See From Cicero to Aquinas to Jefferson, the Long Road of Natural Law. The Scottish influence was one current among others. But it fit. A people who thought that ordinary persons could see basic truths could also believe, without embarrassment, that ordinary persons could govern themselves.

And the Declaration's own method shows it. The long list of grievances against the king is stated in plain language, one at a time, and the Declaration says it wants to "submit" those facts "to a candid world." The assumption is that a fair-minded reader, with no special training, can judge. The document is addressed to everyone.

What this has to do with conservatives

Here is why this matters beyond intellectual history. Conservatives tend to trust ordinary people's judgment, and they tend to distrust the expert who says the ordinary person must be overruled. The Reid-Witherspoon line is part of the foundation for that trust.

Three examples.

1. The jury. The Sixth and Seventh Amendments guarantee trial by jury, ordinary citizens deciding the facts of a case. The premise is that common sense, applied to evidence, is a reliable instrument. If you thought only trained experts could judge a fact, you would abolish the jury. The Framers put it in the Constitution twice.
2. The vote. Self-government is the claim that the people can be trusted with the choice of those who govern them. Federalist 1 opens by asking "whether societies of men are really capable or not of establishing good government from reflection and choice, or whether they are forever destined to depend for their political constitutions on accident and force." Reflection and choice, the work of ordinary reason, are the premise of the whole project.
3. The text. The Constitution was written to be read. Its prose is plain, and the people who ratified it did so in state conventions after reading and arguing about it, including in the essays of the Federalist. Conservatives who argue for reading the document by its ordinary meaning are in the same tradition: a law that the citizen cannot understand is not a law he can obey or consent to.

Contrast that with a mode of thought that treats ordinary perception as a delusion to be corrected by experts. I do not say that expertise is worthless. A surgeon knows things the patient does not, and an engineer knows things the passenger does not. The point is that expertise is built on common sense, and a specialist who contradicts what every sane person can see should be asked to show his work. Sowell's Two Visions Explain Why Smart People Talk Past Each Other makes the case that there is a long-running split between those who trust the dispersed judgment of many and those who trust a vanguard.

The best objection

A fair critic has a good reply. Common sense, he says, has been wrong about many things. It once told everyone that the sun goes around the earth. It told people that the strong have a right to rule, that disease came from bad air and that the world was flat. If common sense is the standard, then error is baked in.

Answer it honestly, in three points.

1. Reid did not claim that every popular belief is a first principle. He claimed that a small set of basic convictions, the existence of the external world, the reality of other minds, the distinction of right from wrong, are the ground of all inquiry. The sun's motion is not one of them. It is a belief about the world, tested and corrected by observation, and common sense in the proper sense is the faculty that does the testing.
2. Science corrects particular beliefs by using the faculties common sense trusts. Astronomers who showed that the earth moves did it with eyes, instruments and arithmetic, all things the ordinary mind relies on. They did not throw out perception. They used it more carefully.
3. The alternative is worse. If the ordinary person's judgment counts for nothing, then someone else's judgment must count for everything, and the question becomes who gets to be that someone. Every case for overriding ordinary judgment ends in a claim that a particular group knows better. History does not suggest that group is humble.

Reid himself was careful on this point. His complaint against Hume was not that Hume was too careful but that he left the careful procedure and abandoned the evidence of his own senses, which he used every day.

Why it still bites

The idea has a modern application. When someone tells you that a policy has worked while your own eyes show you empty shelves, or that words mean the opposite of what they have always meant, or that you cannot tell a plain fact because you lack a credential, the common sense tradition says you are entitled to hesitate. See C. S. Lewis Warned About Men Without Chests in a Book About Schoolbooks, where C. S. Lewis argued that a certain way of "debunking" values leaves a people without the means to resist anything, and Equity Versus Equality, Why Swapping One Word Changes Everything for what happens when a familiar word is stretched until the plain meaning breaks.

This is not a license for laziness. Plain talk, in the Founding sense, means disciplined clarity: say what you mean, give your reasons and let the reader judge. The Founders were among the most widely read people of their age, and they wrote plainly on purpose, since they were addressing a country of farmers, tradesmen and lawyers and expected them to follow the argument.

The case in brief

1. Common sense, in the philosophical sense, is the claim that ordinary people know the real world and basic moral truths directly and do not need a philosopher's license.
2. Thomas Reid answered Hume's skepticism in 1764 by denying the "way of ideas" and treating first principles as the starting point of thought, not the casualties of argument.
3. John Witherspoon brought Scottish common sense thinking to Princeton in 1768, taught James Madison, and signed the Declaration of Independence in 1776.
4. The Declaration's self-evident truths, the jury, the vote and a constitution written to be read all assume that ordinary reason is a reliable instrument of self-government.
5. Common sense is not infallible, but it is the faculty that tests every other claim, and an expert who contradicts what every sane person can see should be asked to show his work.

What you can do: read the first two paragraphs of the Declaration of Independence at the Constitution page beside it, and next time you are called for jury duty, go.