Deductive vs Inductive Reasoning
Farnam Street (Shane Parrish) · 2018
"Deduction moves from general premises to a certain conclusion (if the premises are true, the conclusion must be true); induction moves from specific observations to a probable — never certain — general conclusion, and confusing the two (treating an inductive leap as if it had deductive certainty) is a common source of bad reasoning."
Deductive reasoning starts from a general premise assumed true (all men are mortal), applies a specific case (Socrates is a man), and reaches a conclusion that must be true if the premises are (Socrates is mortal) — it's binary, either valid or invalid. Inductive reasoning draws a general or probable conclusion from specific observations (all the swans I've seen are white, so swans are probably white) — it's a matter of degree (strong or weak), never certain, and always open to revision by a single disconfirming case (a black swan).
Karl Popper's theory of falsification builds directly on this distinction: since induction can never fully prove a general claim (no matter how many white swans you've seen, the next one could be black), Popper argued science should instead use deduction to derive falsifiable predictions from a hypothesis and then aggressively try to disprove them — a theory earns provisional acceptance not by being 'proven' but by surviving repeated, genuine attempts at falsification.
According to this article, what kind of reasoning is Sherlock Holmes actually using in his famous 'deductions,' despite the popular label?
Read more about the topic
The explanation above is written with AI assistance. These are the originals — go to them to check it.
- Peter Cathcart Wason and the theory of falsification (related Farnam Street piece)Farnam Street
- The Three Buckets — Lessons of History (Durant)Farnam Street
16 Mental Models to Sharpen Your Thinking
"A compact reference of sixteen widely-used mental models — spanning economics, psychology, and systems thinking — intended as a checklist to apply against a decision rather than a single unifying theory."