Character guide

Immanuel Kant

supporting

Also known as Kant

Kant arrives in Russell's argument at the moment the problem of a priori knowledge becomes acute: how can we know, before meeting them, that any two future Londoners plus two more will make four? His answer—that space, time, and causality are contributions of our own nature, while the 'thing in itself' stays forever out of reach—is the boldest solution on offer. Russell admires its ingenuity even as he dismantles it, making Kant the indispensable sparring partner for anyone who wants to see how far the mind's furniture can be trusted.

Descartes

supporting

Descartes sets the tone for the whole inquiry: the opening question of whether any knowledge is certain enough that no reasonable man could doubt it is essentially his. His method of doubt turns the familiar table, the sun, the chair beneath us into problems, and his cogito becomes the first foothold Russell tests rather than simply accepts. He matters because he makes radical doubt feel like a procedure rather than a mood—and because the book's early chapters are, in effect, a running conversation with his demand for foundations.

Bishop Berkeley

supporting

Also known as Berkeley

Berkeley holds that colours, sounds, and shapes cannot exist apart from a mind, since what we apprehend is always an 'idea.' Russell grants the force of the position and then locates its flaw: Berkeley confuses the act of apprehension, which is mental, with the object apprehended, which need not be. The distinction matters enormously, because on it rests the mind's whole power to be acquainted with something other than itself. Berkeley is the book's most instructive wrong turn—wrong in a way that sharpens what knowledge actually is.

Plato

supporting

Plato stands behind Russell's discussion of universals, the realm of abstract entities that mathematics and language seem to require. His vision of an open world of free possibilities—where much remains unknown because there is so much to know—echoes through the book's closing reflections on why philosophy is worth studying at all. He matters because he supplies the alternative to pure empiricism: the idea that some things are known not by encounter but by reason, and that this knowledge is what gives unity to the sciences.

Socrates

minor

Classical Greek philosopher referenced in discussions of universals.

Leibniz

minor

Rationalist philosopher whose principle of sufficient reason is mentioned.

Hume

supporting

Hume is the quiet destabilizer of the book's middle chapters: if all knowledge comes from experience, what justifies our confidence that the sun will rise tomorrow or that one event causes another? Russell treats Hume's skepticism not as a dead end but as the honest residue that philosophy must confront, and his questions about induction and causation shape the problem of our knowledge of the external world. He matters because he shows how far empiricism can go before it begins to undermine itself—and because Russell's own answers are measured against that limit.

Hegel

minor

German idealist philosopher briefly critiqued for his view of reality.

Charles I

minor

Also known as Charles

English king used as an example of historical knowledge.

Bismarck

minor

German statesman used as an example in knowledge by description.

Othello

minor

Shakespearean character used as an example of acquaintance.

Desdemona

minor

Shakespearean character used as an example of acquaintance.

Cassio

minor

Shakespearean character used as an example of acquaintance.

George IV

minor

British king used as an example in a logical puzzle.

Jones

minor

Hypothetical person used in examples about knowledge.

Brown

minor

Hypothetical person used in examples about knowledge.

Robinson

minor

Hypothetical person used in examples about knowledge.

Smith

minor

Hypothetical person used in examples about knowledge.

Hylas

minor

Fictional interlocutor in Berkeley's dialogues, referenced in discussion.

Julius Caesar

minor

Roman emperor used as an example in knowledge by description.