What an Argument Actually Is
Most disagreements aren't arguments — they're assertions taking turns
An argument, in the logical sense, is a set of premises offered in support of a conclusion. That's it.
- An argument is premises offered in support of a conclusion — not a fight or an assertion
- Two independent ways to object: the premises are false, or the conclusion doesn't follow
- An argument can be flawlessly logical and worthless because a premise is false
Aristotle's great insight, roughly 2,300 years ago, was that you can evaluate the form of reasoning separately from its content. He noticed that 'All A are B; all B are C; therefore all A are C' is reliable no matter what you substitute for A, B, and C. That let him build the first system for checking reasoning mechanically — the syllogism — and it produced the distinction logic still runs on: an argument…
Why it matters: Aristotle separated an argument's form from its content, giving us validity (does the conclusion follow?) and soundness (are the premises also true?). Most confused disagreements are people attacking one while the other is the real problem.Choose one real claim or decision today and test it against this idea: An argument is premises offered in support of a conclusion — not a fight or an assertion
Attacking the Person Instead of the Argument
Even someone you despise can be right
An ad hominem fallacy attacks the person making an argument rather than the argument itself. 'You're only saying that because you're rich,' 'she has no credentials,' 'look at his history' — none of these engage the claim.
- Ad hominem attacks the person instead of engaging the argument
- A dishonest or unpleasant person can still be right — merit is independent of who holds it
- Not a fallacy when someone offers testimony rather than reasoning: then credibility is the evidence
Naomi Oreskes and Erik Conway's Merchants of Doubt documents how the tobacco industry, facing mounting evidence linking smoking to cancer, ran a strategy that rarely tried to refute the science directly. Instead, industry-funded groups attacked the scientists — questioning their motives, funding, and competence — and amplified a small number of contrarian scientists whose credibility was invoked against the mass of evidence. An internal Brown & Williamson memo from 1969 stated the strategy with…
Why it matters: Ad hominem persists because it works: the tobacco industry built a decades-long strategy on attacking scientists rather than evidence. The test is whether reasoning was offered — if so, the person is irrelevant; if only testimony, credibility is fair game.Choose one real claim or decision today and test it against this idea: Ad hominem attacks the person instead of engaging the argument
Not All Evidence Is Equal
A hierarchy that resolves most 'but I read a study' arguments
'A study found... ' means almost nothing without knowing what kind of study.
- 'A study found' is meaningless without knowing the study type
- Anecdotes sit at the bottom — vivid, memorable, and nearly worthless for general claims
- Observational studies find correlation; randomized trials can establish causation
The Scottish doctor Archie Cochrane spent part of World War II as a prisoner of war, serving as a medical officer in camps with almost no supplies. The experience left him with a lasting suspicion: he was treating people with confidence in remedies he had no evidence actually worked, and he could not tell whether his patients recovered because of him or despite him. In 1972 he published a book arguing that medicine had…
Why it matters: The evidence hierarchy exists because clinical intuition and tradition demonstrably got things wrong for decades. Cochrane's insight — that we often can't tell if a treatment works without randomization — reshaped medicine and applies to any empirical claim.Choose one real claim or decision today and test it against this idea: 'A study found' is meaningless without knowing the study type
False Dilemmas and Slippery Slopes
Two of the most common ways an argument smuggles in a hidden assumption
A false dilemma presents two options as if they were the only ones. 'Either we cut this program or the country goes bankrupt.
- A false dilemma presents two options as exhaustive when more exist
- The frame does the arguing — reject the frame rather than picking a side
- A slippery slope asserts an inevitable chain without establishing the mechanism
The false dilemma is powerful precisely because it hides its work in the setup rather than the conclusion. Logicians classify it among the informal fallacies — errors not of form but of content, where the argument's structure may be flawless while a premise quietly smuggles in something false. The premise 'there are only two options' is rarely stated outright, which is what makes it hard to attack: an audience given a binary choice tends…
Why it matters: Both fallacies hide their work in an unstated premise — 'these are the only options' or 'this leads inevitably there.' The fix is the same: attack the smuggled premise directly rather than debating within the frame it created.Choose one real claim or decision today and test it against this idea: A false dilemma presents two options as exhaustive when more exist
Sources, Consensus, and When to Trust Experts
You can't verify everything yourself — so verify the process instead
You cannot personally evaluate the primary literature on vaccines, climate, monetary policy, and structural engineering. Nobody can.
- Deferring to expertise isn't a fallacy — you cannot verify everything personally
- It becomes fallacious outside the expert's field, against their field's consensus, or in place of evidence
- Consensus is stronger than any individual expert because of independent competing scrutiny
Naomi Oreskes ran a straightforward test of whether scientific consensus on climate change actually existed, given persistent media framing of an ongoing debate. She examined 928 peer-reviewed papers published between 1993 and 2003 whose abstracts matched 'global climate change' and found that not one disputed the consensus position. Her 2004 Science paper contrasted this with media coverage, which routinely presented the issue as evenly contested. Her later book with Erik Conway explained the gap:…
Why it matters: Consensus derives its weight from many independent researchers competing to disprove each other. Oreskes found zero of 928 climate papers disputing consensus while media portrayed a debate — the lone-contrarian frame is compelling precisely because it's exploitable.Choose one real claim or decision today and test it against this idea: Deferring to expertise isn't a fallacy — you cannot verify everything personally
Bayesian Thinking: Update, Don't Flip
Beliefs should have dials, not switches
Most people treat beliefs as binary — you believe something or you don't — and change them by flipping. Bayesian reasoning treats beliefs as probabilities and evidence as something that shifts them by an amount proportional to how strong it is.
- Beliefs are probabilities to update, not switches to flip
- How much evidence should move you depends on your prior probability
- Base rate neglect: a 95% accurate test for a 1-in-1,000 disease still means ~2% odds after a positive
In 1978, researchers at Harvard Medical School posed a version of exactly this problem to 60 physicians, residents, and students at four Harvard teaching hospitals: a disease with a 1-in-1,000 prevalence, a test with a 5% false-positive rate, a patient who tests positive and has no symptoms. What's the probability the patient actually has the disease? Almost half answered 95%. The correct answer is about 2%. Only around a fifth of these highly trained…
Why it matters: Evidence should move belief in proportion to its strength and the prior probability. Harvard doctors got a base-rate problem wrong by a factor of nearly 50, which is why this error matters far beyond textbooks.Choose one real claim or decision today and test it against this idea: Beliefs are probabilities to update, not switches to flip