Major World Philosophers
(c. 500 - 428 B.C.). Greek Presocratic philosopher
who is said to have made Athens the center of
philosophy and to have been Socrates' teacher; he
rejected the four elements theory of Empedocles and
posited instead an infinite number of unique
particles of which all objects are composed.
(1033 - 1109). Italian monk and Scholastic
theologian who became archbishop of Canterbury. St.
Anselm founded Scholasticism, integrated
Aristotelian logic into theology, and believed that
reason and revelation are compatible. He is most
famous for his influential ontological argument for
Aquinas, St. Thomas
(1225 - 74). The greatest thinker of the Scholastic
School. His ideas were, in 1879, made the official
Catholic philosophy. He incorporated Greek ideas
into Christianity by showing Aristotle's thought
to be compatible with church doctrine. In his
system, reason and faith (revelation) form two
separate but harmonious realms whose truths
complement rather than oppose one another. He
presented influential philosophical proofs for the
existence of God.
(384 - 322 B.C.). Greek philosopher, scientist,
logician, and student of many disciplines.
Aristotle studied under Plato and became the tutor
of Alexander the Great. In 335 he opened the
Lyceum, a major philosophical and scientific school
in Athens. Aristotle emphasized the observation of
nature and analyzed all things in terms of "the
four causes." In ethics, he stressed that virtue
is a mean between extremes and that man's highest
goal should be the use of his intellect. Most of
Aristotle's works were lost to Christian
civilization from the fifth through the twelfth
Augustine of Hippo, St.
(354 - 430). The greatest of the Latin church
fathers and possibly the most influential Christian
thinker after St. Paul. St. Augustine emphasized
man's need for grace. His Confessions and The City
of God were highly influential.
(1126 - 98). Spanish-born Arabian philosopher,
lawyer, and physician whose detailed commentaries
on Aristotle were influential for over 300 years.
He emphasized the compatibility of faith and reason
but believed philosophical knowledge to be derived
from reason. The Church condemned his views.
(980 - 1037). Islamic medieval philosopher born in
Persia. His Neoplatonist interpretation of
Aristotle greatly influenced medieval philosophers,
including St. Thomas Aquinas. Avicenna was also a
physician; his writings on medicine were important
for nearly 500 years.
Bacon, Sir Francis
(1561 - 1626). English statesman, essayist, and
philosopher, one of the great precursors of the
tradition of British empiricism and of belief in
the importance of scientific method. He emphasized
the use of inductive reasoning in the pursuit of
(c. 475 - 535). Roman statesman, philosopher, and
translator of Aristotle, whose Consolation of
Philosophy (written in prison) was widely read
throughout the Middle Ages; it showed reason's role
in the face of misfortune and was the link between
the ancient philosophers and the Scholastics.
(1596 - 1650). French philosopher and scientist,
considered the father of modern philosophical
inquiry. Descartes tried to extend mathematical
method to all knowledge in his search for
certainty. Discarding the medieval appeal to
authority, he began with "universal doubt," finding
that the only thing that could not be doubted was
his own thinking. The result was his famous
"Cogito, ergo sum," or "I think, therefore I am."
(1859 - 1952). Leading American philosopher,
psychologist, and educational theorist. Dewey
developed the views of Charles S. Peirce (1839 -
1914) and William James into his own version of
pragmatism. He emphasized the importance of inquiry
in gaining knowledge and attacked the view that
knowledge is passive.
Hegel, Georg Wilhelm Friedrich
(1770 - 1831). German philosopher whose idealistic
system of metaphysics was highly influential; it
was based on a concept of the world as a single
organism developing by its own inner logic through
trios of stages called "thesis, antithesis, and
synthesis" and gradually coming to embody reason.
Hegel held the monarchy to be the highest
development of the state.
(1889 - 1976). German philosopher who studied with
Husserl. Heidegger's own philosophy, which was
influenced by Kierkegaard, emphasized the need to
understand "being," especially the unique ways that
humans act in and relate to the world.
(1588 - 1679). English materialist and empiricist,
one of the founders of modern political philosophy.
In the Leviathan, Hobbes argued that because men
are selfish by nature, a powerful absolute ruler
is necessary. In a "social contract," men agree to
give up many personal liberties and accept such
(1711 - 76). British empiricist whose arguments
against the proofs for God's existence are still
influential. Hume held that moral beliefs have no
basis in reason, but are based solely on custom.
(1842 - 1910). American philosopher and
psychologist, one of the founders of Pragmatism,
and one of the most influential thinkers of his
era. James viewed consciousness as actively shaping
reality, defined truth as "the expedient" way of
thinking, and held that ideas are tools for guiding
our future actions rather than reproductions of our
(1724 - 1804). German philosopher, possibly the
most influential of modern times. He synthesized
Leibniz's rationalism and Hume's skepticism into
his "critical philosophy": that ideas do not
conform to the external world, but rather the world
can be known only insofar as it conforms to the
mind's own structure. Kant claimed that morality
requires a belief in God, freedom, and immortality,
although these can be proved neither scientifically
nor by metaphysics.
(1813 - 55). Danish philosopher, religious thinker,
and extraordinarily influential founder of
existentialism. Kierkegaard held that "truth is
subjectivity," that religion is an individual
matter, and that man's relationship to God requires
Leibniz, Gottfried Wilhelm
(1646 - 1716). German philosopher, diplomat, and
mathematician, one of the great minds of all time.
Leibniz was an inventor (with Sir Isaac Newton) of
the calculus and a forefather of modern
mathematical logic. He held that the entire
universe is one large system expressing God's plan.
(1632 - 1704). Highly influential founder of
British empiricism. Locke believed that all ideas
come to mind from experience and that none are
innate. He also held that authority derives solely
from the consent of the governed, a view that
deeply influenced the American Revolution and the
writing of the U.S. Constitution.
(1469 - 1527). Italian Renaissance statesman and
political writer. In The Prince, one of the most
influential political books of modern times,
Machiavelli argues that any act of a ruler designed
to gain and hold power is permissible. The term
Machiavellian is used to refer to any political
tactics that are cunning and power-oriented.
(1135 - 1204). Spanish-born medieval Jewish
philosopher and thinker. Maimonides tried to
synthesize Aristotelian and Judaic thought. His
works had enormous influence on Jewish and
(1818 - 83). German revolutionary thinker, social
philosopher, and economist. His ideas, formulated
with Engels, laid the foundation for
nineteenth-century socialism and twentieth-century
communism. Although Marx was initially influenced
by Hegel, he soon rejected Hegel's idealism in
favor of materialism. His Communist Manifesto and
Das Kapital are among the most important writings
of the last 200 years.
Mill, John Stuart
(1806 - 73). English empiricist philosopher,
logician, economist, and social reformer. His
System of Logic described the basic rules for all
scientific reasoning. As a student of Jeremy
Bentham, he elaborated on utilitarian ethics; in
On Liberty, he presented a plea for the sanctity
of individual rights against the power of any
Moore, G. E. (George Edward)
(1873 - 1958). British philosopher who emphasized
the "common sense" view of the reality of material
objects. In ethics, Moore held that goodness is a
quality known directly by moral intuition and that
it is a fallacy to try to define it in terms of
More, Sir Thomas
(1478 - 1535). A leading Renaissance humanist and
statesman, Lord Chancellor of England. More was
beheaded for refusing to accept the king as head
of the Church. Influenced by Greek thinking, he
believed in social reform and drew a picture of an
ideal peaceful state in his Utopia.
Nietzsche, Friedrich Wilhelm
(1844 - 1900). German philosopher, philologist,
and poet. As a moralist, he rejected Christian
values and championed a "Superman" who would create
a new, life-affirming, heroic ethic by his "will
(1623 - 62). French philosopher, mathematician,
scientist, and theologian. His posthumous Pensees
("Thoughts") argues that reason is by itself
inadequate for man's spiritual needs and cannot
bring man to God, who can be known only through
(c. 428 - c. 348 B.C.). Athenian father of Western
philosophy and student of Socrates, after whose
death he traveled widely. On returning to Athens,
he founded an Academy, where he taught until he
died. His writings are in the form of dialogues
between Socrates and other Athenians. Many of
Plato's views are set forth in The Republic, where
an ideal state postulates philosopher kings,
specially trained at the highest levels of moral
and mathematical knowledge. Plato's other works
analyzed moral virtues, the nature of knowledge,
and the immortality of the soul. His views on
cosmology strongly influenced the next two thousand
years of scientific thinking.
(205 - 270). Egyptian-born founder of Neoplatonism,
who synthesized the ideas of Plato and other Greek
philosophers. Plotinus believed all reality is
caused by a series of outpourings (called
emanations) from the divine source. Although not
himself a Christian, he was a major influence on
Rousseau, Jean Jacques
(1712 - 78). Swiss-French thinker, born in Geneva.
Rousseau has been enormously influential in
political philosophy, educational theory, and the
Romantic movement. In The Social Contract (1762),
he viewed governments as being expressions of the
people's "general will," or rational men's choice
for the common good. Rousseau emphasized man's
(1872 - 1970). English philosopher and logician
influential as an agnostic and a pacifist. Early
work with Alfred North Whitehead gave birth to
modern logic. Russell changed his views numerous
times but always sought to establish philosophy,
especially epistemology, as a science.
(1863 - 1952). Spanish-born American philosopher
and poet; a student of William James. Santayana
attempted to reconcile Platonism and materialism,
studied how reason works, and found "animal faith,"
or impulse, to be the basis of reason and belief.
(1905 - 80). French philosopher, novelist, and
dramatist; one of the founders of existentialism.
Sartre was a Marxist through much of his life. He
held that man is "condemned to be free" and to bear
the responsibility of making free choices.
(1788 - 1860). German post-Kantian philosopher who
held that although irrational will is the driving
force in human affairs, it is doomed not to be
satisfied. He believed that only art and
contemplation could offer escape from determinism
and pessimism. Schopenhauer strongly influenced
Nietzsche, Freud, Tolstoy, Proust, and Thomas Mann.
Scotus, John Duns
(c. 1266 - 1308). Scottish-born Scholastic
philosopher who tried to integrate Aristotelian
ideas into Christian theology. Scotus emphasized
that all things depend not just on God's intellect
but on divine will as well.
(1723 - 1790). Scottish philosopher and economist.
He believed that if government left the marketplace
to its own devices, an "invisible hand" would
guarantee that the results would benefit the
populace. Smith has had enormous influence on
economists into the present day.
(464 - 399 B.C.). Athenian philosopher who
allegedly wrote down none of his views, supposedly
from his belief that writing distorts ideas. His
chief student, Plato, is the major source of
knowledge of what is known of his life. Socrates
questioned Athenians about their moral, political,
and religious beliefs, as depicted in Plato's
dialogues; his questioning technique, called
dialectic, has greatly influenced western
philosophy. Socrates is alleged to have said that
"the unexamined life is not worth living." In 399
B.C., he was brought to trial on charges of
corrupting the youth and religious heresy.
Sentenced to die, he drank poison.
Spinoza, Benedict (Baruch)
(1623 - 77). Dutch-born philosopher expelled from
the Amsterdam Jewish community for heresy in 1656;
he was attacked by Christian theologians 14 years
later. In Ethics, Spinoza presents his views in a
mathematical system of deductive reasoning. A
proponent of monism, he held-in contrast to
Descartes-that mind and body are aspects of a
single substance, which he called God or nature.
Voltaire (Francois Marie Arouet)
(1694 - 1778). French philosopher, essayist, and
historian; one of the major thinkers of the
Enlightenment. A Deist who was anti-Christian,
Voltaire widely advocated tolerance of liberal
ideas and called for positive social action. His
novel Cyandide is a parody of the optimism of
Whitehead, Alfred North
(1861 - 1947). British philosopher and
mathematician who worked with Bertrand Russell.
Whitehead tried to integrate twentieth-century
physics into a metaphysics of nature.
William of Ockham (Occam)
(c. 1285 - c. 1349). Franciscan monk and important
English theologian and philosopher. In his
nominalism, he opposed much of the thought of St.
Thomas Aquinas and of medieval Aristotelianism; he
also rejected the Pope's power in the secular
- Abelard, Peter
- (1079 - 1142). French philosopher. One of the most
influential medieval logicians and theologians.
Around 1113, while teaching theology in Paris,
Abelard fell in love with his student Heloise, whom
he secretly married; he was condemned for heresy
a few years later because of his nominalist views
- Jeremy Bentham (1748 - 1832): "The greatest
happiness of the greatest number is the foundation
of morals and legislation."
- Confucius (551 - 479 B.C.): "Hold faithfulness and
sincerity as first principles."
- Rene Descartes (1596 - 1650): "Cogito, ergo sum"
(Latin for "I think, therefore I am").
- Thomas Hobbes (1588 - 1679): "The life of a man (in
a state of nature) is solitary, poor, nasty,
brutish, and short."
- Immanuel Kant (1724 - 1804): "Happiness is not an
ideal of reason but of imagination."
- John Locke (1632 - 1704): "No man's knowledge here
can go beyond his experience."
- Niccolo Machiavelli (1469 - 1527): "God is not
willing to do everything, and thus take away our
free will and that share of glory which belongs to
- John Stuart Mill (1806 - 73): "Liberty consists in
doing what one desires."
- Plato (428 - 348 B.C.): "The life which is
unexamined is not worth living."
- Bertrand Russell (1872 - 1970): "It is undesirable
to believe a proposition when there is no ground
whatever for supposing it true."
- Seneca (c. 4 B.C. - A.D. 65): "Even while they
teach, men learn."
- Socrates (c. 470 - 399 B.C.): "There is only one
good, knowledge, and one evil, ignorance."
- Voltaire (1694 - 1778): "If God did not exist, it
would be necessary to invent Him."
How to Argue Logically
We like to think that we speak logically all the
time, but we are aware that we sometimes use
illogical means to persuade others of our point of
view. In the heat of an impassioned argument, or
when we are afraid our disputant has a stronger
case, or when we don't quite have all the facts
we'd like to have, we are prone to engage in faulty
processes of reasoning, using arguments we hope
will appear sound.
Such defective arguments are called fallacies by
philosophers who, starting with Aristotle, have
catalogued and classified these fallacious
arguments. There are now over 125 separate
fallacies, most with their own impressive-sounding
names, many of them in Latin.
Some arguments have easily recognizable defects.
For instance, in the argument ad hominem, a
person's views are criticized because of a
logically irrelevant personal defect: "You can't
take Smith's advice on the stock market; he's a
known philanderer." In the genetic fallacy,
something is mistakenly reduced to its origins: "We
know that emotions are nothing more than
physiology; after all, medical research has shown
emotions involve the secretion of hormones."
Another illogical argument is named for the
erroneous thinking a wagering person may fall prey
to, the gambler's fallacy (also called the Monte
Carlo fallacy): "I'm betting on heads; it's got to
come up since we've just had nine straight tails."
Some fallacies may not be recognized as erroneous
reasoning because they are such commonly used forms
of argument. For instance, if we say, "I'm sure my
cold is due to the weather; I started sneezing
right after it went from 60 degrees to 31 degrees
in three hours," we are committing the fallacy with
the Latin name of post hoc ergo propter hoc ("after
this, therefore because of this"). Many a political
argument exemplifies the fallacy of arguing in a
circle; for instance: "Only wealthy men are capable
of leading the country; after all, leadership can
be learned only if you have had money to exercise
power." Many prejudicial or stereotypical arguments
commit the fallacy of division, or of applying to
the part what may be true of the whole: "North
Dakota has wide-open spaces; since Jack's farm is
there, it must be quite large." The converse of
this is the fallacy of composition, where
properties of the parts are erroneously attributed
to the whole: "Every apple on this tree is rotten;
therefore, the tree itself is hopelessly diseased."
It may be a surprise to realize that some widely
accepted forms of argument are just as fallacious
as the most logically defective reasoning. When we
appeal to the beliefs or behavior of the majority
to prove the truth of something, we are committing
the fallacy of consensus gentium: "Imbibing alcohol
cannot be bad for people, since all cultures
studied have used alcohol." Or consider the person
who argues that "Tragedy is the highest form of
literature; after all, didn't Aristotle consider
it such?" This is a form of the fallacy of arguing
from authority. There is also the fallacy of
ignoratio elenchus, which has nothing to do with
ignorance; its name means that the point made is
irrelevant to the issue at hand, as in the
untenable view of a lawyer who says, "Ladies and
gentlemen of the jury, you cannot convict my client
of manslaughter while driving under the influence;
after all, advertisements for alcohol exist
everywhere in our culture."
In logic, a fallacy is a form of reasoning that is illogical
or that violates the rules of valid argumentation. A
formal fallacy makes strict violations of the rules of
logic. An informal fallacy does not violate the rules of
logic, but it violates the rules of valid reasoning or
arrives at unsound conclusions, because of unsound
A common formal fallacy involves affirming the consequent or
denying the antecedent in hypothetical reasoning. That is,
if A, then B, affirming B as the proof of A, or denying A
as the basis for denying B. In either case, it does not
follow that the affirmation or the denial proves what is
claimed. Thus, if all Americans are bald (A), then all
Americans require no hairdressers (B)--the affirmation of
B, that is, saying it is true, does not prove A; neither
does the denial of A prove the denial of B.
Two other kinds of formal fallacies that are important are
the argument from the undistributed middle and the
conversion of a universal positive proposition. In the
first, it is argued that "all A is B" and "all C is B";
therefore, "all A is C." If "Americans" is substituted for
"A", "human beings" for "B", and "Hungarians" for "C", it
is easily seen that the argument is fallacious. In the
other case, it is argued that if "all A is B," then "all B
is A"; this is obviously fallacious if the same
substitutions are made.
Because informal fallacies occur much more frequently in
ordinary discussions, in political speeches, and in
advertising, they are, in some ways, more important. Some
of these fallacies are a result of the ambiguity of the
terms used; people often slip unconsciously from one
meaning of a term to another. Other major informal
fallacies are the ignoratio elenchi, that is, arguing for
something different from the question asked; and the tu
quoque argument, in which an unsound argument is justified
by claiming the unsoundness of another. These soon
degenerate into the argument ad hominem, in which the
argument of an opponent is countered by pointing to his or
her personal faults rather than by considering the
substance of the argument; and the argument from
authority, which appeals to famous or important people who
agree with a particular point of view.
Richard H Popkin
Engel, S. Morris, With Good Reason: An
Introduction to Informal Fallacies, 3d ed. (1985);
Fearnside, W. Ward, and Holther, William B., Fallacy: The
Counterfeit of Argument (1959).
The individual articles presented here were generally first published
in the early 1980s. This subject presentation was first placed
on the Internet in May 1997.
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