Views of knowledge

Thinkers

Each thinker has a page of their own: the view, the argument behind it, and where it meets and parts from Deutsch.

Each entry is marked by its answer to one question: does knowledge need to be justified? Deutsch, following Popper, says no. Compare all views side by side →

A man leans over a celestial globe and an open book at night, lit by a single candle he holds in his hand — Gerrit Dou, *Astronomer by Candlelight*, late 1650s. J. Paul Getty Museum, Los Angeles. One small light, pointed where the question is.Public domain, via Wikimedia Commons.

Ancient

Xenophanesc. 570 – c. 475 BCNo justification
The gods revealed nothing at the start. People search, and in time find better; but no one knows the certain truth.
Socrates and Plato469–399 BC and c. 428–348 BCNeeds justifying
Wisdom begins in knowing that you do not know. Learning is recollection, and knowledge is true belief with an account.
Aristotle384–322 BCNeeds justifying
Science climbs by induction from particulars to first principles, then demonstrates everything else from them.
Sextus Empiricusactive around AD 200Qualified
Every justification needs another. Set each argument against its equal, suspend judgement, and find calm.

Early modern

Francis Bacon1561–1626Needs justifying
Purge the idols of the mind and climb, patiently, from observation to law.
René Descartes1596–1650Needs justifying
Doubt everything that can be doubted, then rebuild on what cannot.
John Locke1632–1704Needs justifying
The mind starts as white paper, and experience writes on it.
David Hume1711–1776Qualified
No argument can justify induction. We expect the future to resemble the past out of habit.
Immanuel Kant1724–1804Needs justifying
The mind does not copy the world. It imposes space, time and cause on whatever it experiences.

Twentieth century

Karl Popper1902–1994No justification
Conjecture and refutation. Science is marked out by falsifiability, and knowledge exists without a knower.
Michael Polanyi1891–1976Qualified
We know more than we can tell. Skill, judgement and commitment carry science, not explicit rules.
W. V. O. Quine1908–2000Qualified
Our beliefs face experience as a whole web, and epistemology becomes a chapter of psychology.
Edmund Gettier1927–2021Needs justifying
Three pages in 1963 showed that a justified true belief can still fail to be knowledge.
Thomas Kuhn1922–1996Qualified
Science alternates between puzzle-solving inside a paradigm and revolutions that replace it.
Imre Lakatos1922–1974Qualified
Judge research programmes, not single theories: a hard core, a protective belt, and progress or decay over time.
Paul Feyerabend1924–1994No justification
No rule of method has survived the history of science. The only principle that never blocks progress: anything goes.
Donald Campbell1916–1996No justification
Blind variation and selective retention, from genes to science: all knowledge grows the way species do.

Contemporary

The Bayesiansfrom Thomas Bayes, c. 1701–1761Needs justifying
Belief comes in degrees, and evidence moves those degrees by Bayes' theorem.
Chiara MarlettocontemporaryNo justification
Physics restated as which transformations are possible and which are not. Knowledge is information that can last.
Brett HallcontemporaryNo justification
The host of ToKCast, who reads Deutsch's books aloud a chapter at a time, and argues that fears of superintelligence rest on a bad theory of knowledge.