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Erasmus, Desiderius (1466-1536)

Dutch humanist. Erasmus produced editions of classical texts far superior to those of the medieval period and, in Diatribe de libero arbitrio (Discourse on Free Will) (1524) defended the moral freedom of individual human beings. The Ecomium moriae id est Laus stultitiae (Praise of Folly) (1509) satirized the political and religious institutions of his time, and many of his Colloquia (1518) are stinging condemnations of ecclesiastical fraud.

Recommended Reading: Christian Humanism and the Reformation: Selected Writings of Erasmus, ed. by John C. Olin (Fordham, 1987) and Erasmus: His Life, Works and Influence, tr. by J. C. Grayson (Toronto, 1996).

Also see SEP, EB, IEP, and ELC.

Eratosthenes (276-197 BCE)

African mathematician who discovered a method for identifying prime numbers and calculated the circumference of the earth. Eratosthenes served for several decades as head of the famous Greek library at Alexandria.

Recommended Reading: P. M. Fraser, Eratosthenes of Cyrene (Oxford, 1972).

Also see EB, WSB, and MMT.


German term for empirical observation.

Erigena, John Scotus (812-877)

Irish philosopher. In De Divisione Naturae (On the Distribution of Nature) (863), Erigena notoriously combined Greek and neoplatonic elements into a highly rationalized scheme in which everything both emanates from and later is reabsorbed by god. Although the divine is incomprehnsible for Erigena, god may be known indirectly, as manifested in the created order. The views on human freedom he defended in De praedestinatione (On Predestination) (851) earned for Erigena the official condemnation of the church.

Recommended Reading: Deirdre Carabine, John Scottus Eriugena (Oxford, 2000); Henry Bett, Johannes Scotus Erigena: A Study in Medieval Philosophy (Hyperion, 1979); and Thomas Duddy, A History of Irish Thought (Routledge, 2002).

Also see EB, SEP, and ELC.


German term for experience generally.

ερος [eros]

Greek personification of love; hence, sexual desire or love generally. Plato's Symposium offers a set of speeches on the nature of love in human life.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967); Louis A. Ruprecht, Jr., Symposia: Plato, the Erotic, and Moral Value (SUNY, 1999); and Jamey Hecht, Plato's Symposium: Eros and the Human Predicament (Twayne, 1999).

Also see Brian Mooney, and PP.

esse est percipi

Latin phrase meaning "to be is to be perceived." According to Berkeley, this is the most basic feature of all sensible objects; for spirits, on the other hand, esse est percipere ("to be is to perceive"). Granting this to be the most fundamental principle of idealistic philosophy, Moore argued that it is indefensible.

Recommended Reading: George Berkeley, Principles of Human Knowledge / Three Dialogues Between Hylas and Philonous, ed. by Roger Woolhouse (Penguin, 1988) and Kenneth P. Winkler, Berkeley: An Interpretation (Clarendon, 1994).

essence / accident {Lat. per se / per accidens}

Distinction among the attributes, properties, or qualities of substances. A thing's possession of its essential properties is necessary either for its individual existence or, at least, for its membership in a specific kind. Accidental features, by contrast, are those which the thing merely happens to have, even though it need not. Thus, for example, rationality may be part of the essence of any human being, but being able to calculate square roots accurately in one's head is (surely) an accident.

The legitimacy of the distinction itself is called into question by philosophers ("anti-essentialists") who doubt whether any features are genuinely essential to the things that have them.

Recommended Reading: Charlotte Witt, Substance and Essence in Aristotle: An Interpretation of Metaphysics vii-ix (Cornell, 1994); Saul A. Kripke, Naming and Necessity (Harvard, 1982); and Garth L. Hallett, Essentialism: A Wittgensteinian Critique (SUNY, 1991).

Also see SEP.


Withdrawal from things or people; see alienation.

eternal return

Belief that everything that happens has happened before and will happen again, since the universe (or time itself) is fundamentally cyclical. A standard feature of Pythagorean and Stoic thought, this view was more recently adopted as a basis for practical hope by Nietzsche.

Recommended Reading: Joan Stambaugh, Nietzsche's Thought of Eternal Return (Taylor & Francis, 1988) and Mircea Eliade, Myth of the Eternal Return, tr. by Willard R. Trask (Princeton, 1971).


Branch of philosophy concerned with the evaluation of human conduct. Philosophers commonly distinguish:

  • descriptive ethics, the factual study of the ethical standards or principles of a group or tradition;
  • normative ethics, the development of theories that systematically denominate right and wrong actions;
  • applied ethics, the use of these theories to form judgments regarding practical cases; and
  • meta-ethics, careful analysis of the meaning and justification of ethical claims.

Recommended Reading: Lawrence M. Hinman, Ethics: A Pluralistic Approach To Moral Theory (Harcourt, 1997); A Companion to Ethics, ed. by Peter Singer (Blackwell, 1993); Bernard Williams, Morality: An Introduction to Ethics (Cambridge, 1993); D. D. Raphael, Moral Philosophy (Oxford, 1994); John M. Rist, Real Ethics: Reconsidering the Foundations of Morality (Cambridge, 2002); James Rachels, The Elements of Moral Philosophy (McGraw-Hill, 2000); and The Blackwell Guide to Ethical Theory, ed. by Hugh Lafollette (Blackwell, 1999).

Also see Ethics Updates, SEP, EB, and IEP.

εθος [ethos]

Greek word for custom or habit, the characteristic conduct of an individual human life. Hence, beginning with Aristotle, ethics is the study of human conduct, and the Stoics held that all behavior—for good or evil—arises from the εθος of the individual.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967).

Also see PP.

Euclid (365-300 BCE)

Greek mathematician whose Elementae (Elements) offered an axiomatic system for geometry based only on a few "common notions" and five basic postulates:

  1. Any two points can be joined by a unique straight line.
  2. A straight line can be extended indefinitely in either direction.
  3. From a center point, a circle can be drawn with any radius.
  4. All right angles are equal to each other.
  5. If two straight lines crossing a third form angles less than two right angles on one of its sides, then indefinite extensions of these lines eventually meet.
Although rejection of the fifth postulate eventually led to the development of alternative geometries by Lobachevsky and Riemann, Euclid's emphasis on axiomatic structure remained significant for mathematicians like Peano and Hilbert and served as a significant model for such philosophers as Hobbes and Spinoza.

Recommended Reading: Thomas L. Heath, History of Greek Mathematics: From Thales to Euclid (Dover, 1981).

Also see MMT, EB, WSB,and ELC.


An approach to ethics (as proposed, for example, by Aristotle or the Stoics) that aims at the achievement of a good life. Classical eudaemonism is concerned with satisfying the objective conditions of happiness {Gk. ευδαιμονια [eudaimonia]}, rather than with pursuing the subjective experience of pleasure. Kant condemned this approach to human conduct as heteronomous.

Recommended Reading: Aristotle, Kant, and the Stoics: Rethinking Happiness and Duty, ed. by Stephen Engstrom and Jennifer Whiting (Cambridge, 1998); J. L. Ackrill, Aristotle on Eudaimonia (Oxford, 1972); and Don Asselin, Human Nature and Eudaimonia in Aristotle (Peter Lang, 1989).

Also see EB, ISM, and PP.

Euler, Leonhard (1707-1783)

Swiss mathematician and physicist; author of Introductio in analysin infinitorum (Introduction to infinite analyses) (1748) and many other mathematical treatises. Euler made significant contributions to the development of number theory, introduced the use of many now-familiar mathematical symbols, and devised (a century before Venn) a convenient set of topographical diagrams for representing the logical relationships expressed in categorical propositions and syllogisms. Euler's chief accomplishments are expressed in non-technical language in the Lettres à une princesse d'Allemnagne (Letters for a German Princess) (1772).

Recommended Reading: Leonhard Euler, Foundations of Differential Calculus, tr. by John D. Blanton (Springer Verlag, 2000); Morris Kline, Mathematical Thought from Ancient to Modern Times (Oxford, 1990); and William Dunham, Euler: The Master of Us All (Math. Assn. of Amer., 1999).

Also see EB, David Wilkins, WSB, and MMT.


Support for the truth of a proposition, especially that derived from empirical observation or experience.

Recommended Reading: Karl R. Popper, Logic of Scientific Discovery (Routledge, 1992).

evil, problem of

Bad things sometimes happen. Whether they are taken to flow from the operation of the world ("natural evil"), to result from deliberate human cruelty ("moral evil"), or simply to correlate poorly with what seems to be deserved ("non-karmic evil"), such events give rise to basic questions about whether or not life is fair.

The presence of evil in the world poses a special difficulty for traditional theists, as both Epicurus and Hume pointed out. Since an omniscient god must be aware of evil, an omnipotent god could prevent evil, and a benevolent god would not tolerate evil, it should follow that there is no evil. Yet there is evil, from which atheists conclude that there is no omniscient, omnipotent, and benevolent god. The most common theistic defense against the problem, propounded (in different forms) by both Augustine and Leibniz, is to deny the reality of evil by claiming that apparent cases of evil are merely parts of a larger whole that embodies greater good. More recently, some have questioned whether the traditional notions of omnipotence and omniscience are coherent.

Recommended Reading: The Problem of Evil: A Reader, ed. by Mark Larrimore (Blackwell, 2000); The Problem of Evil, ed. by Marilyn McCord Adams and Robert M. Adams (Clarendon, 1991); and Richard Swinburne, Providence and the Problem of Evil (Oxford, 1998).

Also see SEP, EB, Peter King, and CE.

excluded middle, principle of

Logical principle that propositions of the form ( p ∨ ~ p ) are tautologous. Thus, for example:

"Either it will snow today or it will not snow today." is necessarily true.

Note the difference between excluded middle and bivalence.

Also see Floy E. Andrews.

exclusive premises

The formal fallacy committed in a categorical syllogism that is invalid because both of its premises are negative.

Example: "Since no mammals are fish and some fish are not whales, it follows that some whales are not mammals."

Also see FF and GLF.


Instantiation in reality, or actual being. Kant pointed out that existence is not a predicate, and Frege proposed that it is a second-order property of those first-order properties that happen to be instantiated. The metaphysical question of what kinds of things exist is the subject of ontology, as is the even more general question of why there is something rather than nothing.

Recommended Reading: Colin McGinn, Logical Properties: Identity, Existence, Predication, Necessity, Truth (Clarendon, 2001); Barry Miller, The Fullness of Being: A New Paradigm for Existence (Notre Dame, 2002); Jean-Paul Sartre, Truth and Existence, tr. by Adrian Van Den Hoven and Ronald Aronson (Chicago, 1995); and Emmanuel Levinas, Existence and Existents, tr. by Robert Bernaeconi (Duquesne, 2001).

Also see SEP.

existential fallacy

The formal fallacy committed in a categorical syllogism that is invalid because it has two universal premises and a particular conclusion.

Example: "All inhabitants of another planet are friendly people, and all Martians are inhabitants of another planet. Therefore, some Martians are friendly people."

Also see GLF.

Existential Generalization

A quantification rule of the form:


	(∃x)( Øx )

Example: "Polly is a bird. Therefore, there is at least one bird."

This pattern of reasoning is one of the basic principles used by proofs in quantification theory.

existential import

The distinguishing feature of propositions that assert the existence of something. In traditional interpretations of categorical logic, all propositions are taken to have existential import, but on a modern interpretation, only the particular propositions, (I and O) have existential import.

Also see EB.

Existential Instantiation

A quantification rule of the form:

	(∃x)( Øx )


Example: "There is at least one bird. Therefore, suppose that some particular thing, z, is a bird."

Properly applied, this pattern of reasoning provides an important basis for proofs in quantification theory.


A (mostly) twentieth-century approach that emphasizes the primacy of individual existence over any presumed natural essence for human beings. Although they differ on many details, existentialists generally suppose that the fact of my existence as a human being entails both my unqualified freedom to make of myself whatever I will and the awesome responsibility of employing that freedom appropriately, without being driven by anxiety toward escaping into the inauthenticity or self-deception of any conventional set of rules for behavior, even though the entire project may turn out to be absurd. Prominent existentialists include Kierkegaard, Heidegger, Jaspers, Beauvoir, Sartre, and Camus.

Recommended Reading: Existentialism: From Dostoevsky to Sartre, ed. by Walter Kaufmann (Meridian, 1988); L. Nathan Oaklander, Existentialist Philosophy: An Introduction (Prentice-Hall, 1995); Robert C. Solomon, Existentialism (McGraw-Hill, 1974); Robert Goodwin, An Introduction to Existentialism (Dover, 1962); and William Barrett, Irrational Man: A Study in Existential Philosophy (Anchor, 1962).

Also see C. S. Wyatt, SEP, and ISM.

expected value

The net return it is reasonable to anticipate as the result of an action or investment. Expected value may be calculated as the sum of the products of each possible outcome and the relative likelihood that it will occur.

Recommended Reading: James T. Fey, Elizabeth D. Phillips, and Catherine Anderson, What Do You Expect?: Probability & Expected Value (Seymour, 1997).


An intelligible account of why something happens. On a covering law model, the scientific explanation of an event has the form of an argument whose conclusion is the event to be explained and whose premises include both antecedent circumstances and one or more hypotheses.

Recommended Reading: Wesley C. Salmon, Causality and Explanation (Oxford, 1997); Richard W. Miller, Fact and Method (Princeton, 1988); Robert W. Batterman, The Devil in the Details: Asymptotic Reasoning in Explanation, Reduction and Emergence (Oxford, 2001); Theories of Explanation, ed. by Joseph C. Pitt (Oxford, 1988); and Peter Lipton, Inference to the Best Explanation (Routledge, 1993).

Also see EB, SEP, DPM, and Dwayne H. Mulder.

Exportation (Exp.)

A rule of replacement of the form:

	[ ( p • q ) ⊃ r ) ] ≡ [ p ⊃ ( q ⊃ r ) ]

Example: "If Harry is tall and quick, then he plays well." is equivalent to "If Harry is tall, then if he's quick, then he plays well."

The reliability of this equivalence is evident from a truth-table.

expressive use of language

Communication that gives vent to feelings, attitudes, or emotions.

Example: "Yeow—hot, hot, hot!."


Having spatial dimensions; the characteristic attribute of anything that occupies space, has shape, is tangible, moves, and is divisible into physical parts.

Also see CE.

extension / intension

Distinction between ways in which the meaning of a term may be regarded: its extension, or denotation, is the collection of things to which the term applies; its intension, or connotation, is the set of features those things are presumed to have in common.

Recommended Reading: D. Alan Cruse, Meaning in Language: An Introduction to Semantics and Pragmatics (Oxford, 2000).

Also see EB.


The feature of a formal system in which the meaning of every non-logical term is wholly determined by its extension; this ensures that compound statments of the system will be truth-functional.

Recommended Reading: Stephen Neale, Facing Facts (Oxford, 2001).


Bearing some relation to something else. See intrinsic / extrinsic.


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