G. E. Moore in the context of "Common sense"

Bertrand Arthur William Russell, 3rd Earl Russell (18 May 1872 – 2 February 1970), was a British philosopher, logician, mathematician, and public intellectual. He influenced mathematics, logic, set theory, and various areas of analytic philosophy.

He was one of the early 20th century's prominent logicians and a founder of analytic philosophy, along with his predecessor Gottlob Frege, his friend and colleague G. E. Moore, and his student and protégé Ludwig Wittgenstein. Russell with Moore led the British "revolt against idealism". Together with his former teacher Alfred North Whitehead, Russell wrote Principia Mathematica, a milestone in the development of classical logic and a major attempt to reduce the whole of mathematics to logic (see logicism). Russell's article "On Denoting" has been considered a "paradigm of philosophy".

Analytic philosophy is a broad movement and methodology within contemporary Western philosophy, especially anglophone philosophy, focused on: analysis as a philosophical method; clarity of prose; rigor in arguments; and making use of formal logic, mathematics, and to a lesser degree the natural sciences. It is further characterized by the linguistic turn, or a concern with language and meaning. Analytic philosophy has developed several new branches of philosophy and logic, notably philosophy of language, philosophy of mathematics, philosophy of science, modern predicate logic and mathematical logic.

The proliferation of analysis in philosophy began around the turn of the 20th century and has been dominant since the latter half of the 20th century. Central figures in its historical development are Gottlob Frege, Bertrand Russell, G. E. Moore, and Ludwig Wittgenstein. Other important figures in its history include Franz Brentano, the logical positivists (especially Rudolf Carnap), the ordinary language philosophers, W. V. O. Quine, and Karl Popper. After the decline of logical positivism, Saul Kripke, David Lewis, and others led a revival in metaphysics.

The theory of sense data is a view in the philosophy of perception, popularly held in the early 20th century by philosophers such as Bertrand Russell, C. D. Broad, H. H. Price, A. J. Ayer, and G. E. Moore. Sense data are taken to be mind-dependent objects whose existence and properties are known directly to us in perception. These objects are unanalyzed experiences inside the mind, which appear to subsequent more advanced mental operations exactly as they are.

Sense data are often placed in a time and/or causality series, such that they occur after the potential unreliability of our perceptual systems yet before the possibility of error during higher-level conceptual analysis and are thus incorrigible. They are thus distinct from the 'real' objects in the world outside the mind, about whose existence and properties we often can be mistaken.

Moral realism (also ethical realism) is the position that ethical sentences express propositions that refer to objective features of the world (that is, features independent of subjective opinion), some of which may be true to the extent that they report those features accurately. This makes moral realism a non-nihilist form of ethical cognitivism (which accepts that ethical sentences express propositions and can therefore be true or false) with an ontological orientation, standing in opposition to all forms of moral anti-realism and moral skepticism, including ethical subjectivism (which denies that moral propositions refer to objective facts), error theory (which denies that any moral propositions are true), and non-cognitivism (which denies that moral sentences express propositions at all). Moral realism's two main subdivisions are ethical naturalism and ethical non-naturalism.

Most philosophers claim that moral realism dates at least to Plato as a philosophical doctrine and that it is a fully defensible form of moral doctrine. A 2009 survey involving 3,226 respondents from mostly English-speaking universities, including mostly faculty members, PhDs and graduate students, found that 56% accept or lean toward moral realism (28%: anti-realism; 16%: other). A 2020 study found that 62.1% accept or lean toward realism. Some notable examples of robust moral realists include David Brink, John McDowell, Peter Railton, Geoffrey Sayre-McCord, Michael Smith, Terence Cuneo, Russ Shafer-Landau, G. E. Moore, John Finnis, Richard Boyd, Nicholas Sturgeon, Thomas Nagel, Derek Parfit, and Peter Singer. Norman Geras has argued that Karl Marx was a moral realist. Moral realism's various philosophical and practical applications have been studied.

A subset of absolute idealism, British idealism was a philosophical movement that was influential in Britain from the mid-nineteenth century to the early twentieth century. The leading figures in the movement were T. H. Green (1836–1882), F. H. Bradley (1846–1924), and Bernard Bosanquet (1848–1923). They were succeeded by the second generation of J. H. Muirhead (1855–1940), J. M. E. McTaggart (1866–1925), H. H. Joachim (1868–1938), A. E. Taylor (1869–1945), and R. G. Collingwood (1889–1943). The last major figure in the tradition was G. R. G. Mure (1893–1979). Doctrines of early British idealism provoked the Cambridge philosophers G. E. Moore and Bertrand Russell to develop the philosophical methodology that gave rise to a new philosophical tradition, analytic philosophy.

The Tractatus Logico-Philosophicus (widely abbreviated and cited as TLP) is the only book-length philosophical work by the Austrian philosopher Ludwig Wittgenstein that was published during his lifetime. The project had a broad goal: to identify the relationship between language and reality, and to define the limits of science. Wittgenstein wrote the notes for the Tractatus while he was a soldier during World War I and completed it during a military leave in the summer of 1918. It was originally published in German in 1921 as Logisch-Philosophische Abhandlung (Logical-Philosophical Treatise). In 1922 it was published together with an English translation and a Latin title, which was suggested by G. E. Moore as homage to Baruch Spinoza's Tractatus Theologico-Politicus (1670).

The Tractatus is written in an austere and succinct literary style, containing almost no arguments as such, but consists of 525 declarative statements altogether, which are hierarchically numbered.

Ordinary language philosophy (OLP, sometimes called linguistic philosophy) is a methodological approach within analytic philosophy which treats many traditional philosophical problems as the result of misunderstandings of how words are ordinarily used. Rather than proposing ideal or artificial languages, ordinary language philosophers investigate the actual use of expressions in everyday contexts, and often argue that once such uses are described carefully, many philosophical "problems" dissolve or change their shape.

In the twentieth century OLP was primarily associated with the later work of Ludwig Wittgenstein, early to mid-century philosophers at the University of Cambridge such as G. E. Moore and John Wisdom, and mid-century philosophers at the University of Oxford, including Gilbert Ryle, J. L. Austin, P. F. Strawson, H. L. A. Hart, and Paul Grice. Because a number of its most prominent practitioners taught at Oxford, OLP is sometimes informally referred to as "Oxford philosophy".

Analytic philosophy is a broad school or style of contemporary Western philosophy, especially anglophone philosophy. It is focused on: analysis as a philosophical method, clarity of prose, and rigor in arguments; making use of formal logic, mathematics, and to a lesser degree the natural sciences. It is further characterized by the linguistic turn, or a concern with language and meaning. Analytic philosophy has developed several new branches of philosophy and logic, notably philosophy of language, philosophy of mathematics, philosophy of science, modern predicate logic and mathematical logic.

The proliferation of analytic philosophy began around the turn of the twentieth century and has been dominant since the second half of the century. Central figures in its history are Gottlob Frege, Bertrand Russell, G. E. Moore, and Ludwig Wittgenstein. Other important figures in its history include Franz Brentano, the logical positivists (especially Rudolf Carnap), and the ordinary language philosophers. Wilfrid Sellars, W. V. O. Quine, Saul Kripke, David Lewis, and others led a decline of logical positivism and a subsequent revival in metaphysics.