Great IdeasKnowing and thinking
Method: how to find things out
Step-by-step ways of reaching the truth, in science and philosophy.
The question
Is there a step-by-step way to find the truth? How did thinkers and scientists learn to find things out?
How the books answer
Oldest first. Each stop is our own short summary of what the author argued; follow the link to the rung for the whole lesson.
c. 350–322 BC
Aristotle, Posterior Analytics
Aristotle says scientific knowledge means proving things from first principles that are true and better known. But those first principles themselves come from experience, by noticing what is general in many cases. So science runs in two directions: up from observation, then down by proof.
“All instruction given or received by way of argument proceeds from pre-existent knowledge.”
c. 300 BC
Euclid, The Elements, Books I–IV
Euclid's method is to state a few definitions and postulates, then prove each step from what came before. Nothing is accepted just because it looks right in the drawing. His method became the model for exact reasoning in many fields.
1620
Francis Bacon, Novum Organum
Bacon argues that science had been stuck for centuries. He warns against the 'idols' of the mind, habits of thought that mislead us, and calls for patient gathering of observations and experiments, then rising slowly to general laws. He compares good scientists to bees, who gather and also transform.
“The bee, a mean between both, extracts matter from the flowers of the garden and the field, but works and fashions it by its own efforts.”
1637
René Descartes, Discourse on the Method (with Rules for the Direction of the Mind)
Descartes gives his method in four rules: accept only what is clear, break problems into parts, go from simple to complex, and review everything. Bacon starts from the senses; Descartes trusts reason and mathematics first. Both wanted a fresh start for knowledge.
1638
Galileo Galilei, Dialogues Concerning the Two New Sciences
Galileo combines experiment and mathematics. He rolls balls down gentle ramps and times them, then finds the mathematical rule: the distance grows as the square of the time. His dialogue shows a new science being argued out step by step.
1687
Isaac Newton, Mathematical Principles of Natural Philosophy
Newton sets out rules for reasoning in natural science: don't invent more causes than you need, and treat what experiments show widely as true until new facts say otherwise. He refused to make up a hidden cause for gravity that he could not find in the evidence.
“But hitherto I have not been able to discover the cause of those properties of gravity from phænomena, and I frame no hypotheses.”
1789
Antoine Lavoisier, Elements of Chemistry
Lavoisier made chemistry a science of careful weighing. He measured everything before and after a reaction and found that the total mass stays the same. Exact measurement settled arguments that words alone had not.
1859
Charles Darwin, On the Origin of Species
Darwin spent over twenty years gathering facts from breeders, fossils, islands and barnacles before publishing. He presented his theory as one long argument, answered the strongest objections he could find, and admitted what he could not explain. His method was patient evidence from many directions.
1902
Henri Poincaré, Science and Hypothesis
Poincaré studies the parts of a scientific theory. Some are facts from experiment, some are useful choices or conventions, and some are guesses waiting to be tested. Hypotheses are necessary, he says, but we should know which kind each one is.
For young readers
A method is a plan for doing something step by step. Scientists use a method to find things out: ask a question, make a guess, test it, and look carefully at what happens.
Galileo wanted to know how things fall. Instead of just arguing, he rolled balls down a ramp and timed them. You can do the same with a toy car, a book and a stopwatch!
Talk about it
- Bacon compared some thinkers to ants, some to spiders and the best to bees. What do you think he meant?
- Design a test: does a heavier ball roll down a ramp faster than a light one?
- Why is it important to measure carefully?
- Darwin worked on his idea for twenty years. Why might he have waited so long?
- What's the difference between a guess and a test?
Where else on the site
- Hypotheses and Controlled Experiments
- Designing Experiments
- Deductive and Inductive Arguments
- Writing a Proof
- Inclined Planes
- Scientific Theories
Every rung tagged with this idea:
- Euclid: Elements, Books I–IV
- Copernicus: On the Revolutions
- Gilbert: On the Loadstone
- Bacon: Novum Organum
- Descartes: Discourse on the Method
- Descartes: The Geometry
- Pascal: The Scientific Treatises
- Newton: The Principia
- Newton: Optics
- Poincaré: Science and Hypothesis
- Planck: Scientific Autobiography
- Weber: Essays in Sociology
These pages are our own short synthesis, written for families. They were inspired by Mortimer J. Adler's Syntopicon, the index of great ideas in volumes 1 and 2 of Great Books of the Western World, but the questions, summaries and groupings are ours, not the Syntopicon's. Short excerpts come from public-domain translations, credited where they appear.