Frederick Charles Copleston, SJ, CBE (10 April 1907 – 3 February 1994) was a Jesuit priest and historian of philosophy.

Copleston's family was Anglican (his uncle, Reginald Stephen Copleston, was a bishop of Calcutta), but he converted to Roman Catholicism while a pupil at Marlborough College, and became a Jesuit in 1929. He studied and later lectured at Heythrop College and, seeing the poor standard of philosophical teaching in seminaries, wrote an influential eleven-volume History of Philosophy (1946–75), which is highly respected.

He is well known for debating the existence of God with Bertrand Russell in a celebrated 1948 BBC broadcast; the following year he debated logical positivism and the meaningfulness of religious language with his friend the analytic philosopher A. J. Ayer.

One of Copleston's most significant contributions to modern philosophy was his work on the theories of St Thomas Aquinas. He attempted to clarify Aquinas's Five Ways (in the Summa Theologica) by making a distinction between in fieri causes and in esse causes. By doing so Copleston makes clear that Aquinas wanted to put forth the concept of an omnipresent God rather than a being that could have disappeared after setting the chain of cause and effect into motion.

Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS (18 May 1872 – 2 February 1970) was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life he considered himself a liberal, a socialist, and a pacifist, but he also admitted that he had never been any of these in any profound sense. He was born in Monmouthshire, into one of the most prominent aristocratic families in Britain.

Russell led the British "revolt against idealism" in the early 20th century. He is considered one of the founders of analytic philosophy along with his predecessor Gottlob Frege and his friend Ludwig Wittgenstein, and is widely held to be one of the 20th century's premier logicians. He co-authored, with A. N. Whitehead, Principia Mathematica, an attempt to ground mathematics on logic. His philosophical essay "On Denoting" has been considered a "paradigm of philosophy." His work has had a considerable influence on logic, mathematics, set theory, linguistics, computer science (see type theory and type system), and philosophy, especially philosophy of language, epistemology, and metaphysics.