Philosophy Pages

    Dictionary    Study Guide  Logic   F A Q s
  History Timeline Philosophers   Locke

Tarski, Alfred (1902-1983)

Polish-American logician who defended a correspondence theory of truth in The Concept of Truth in Formalized Languages (1933) and The Semantic Conception of Truth and the Foundations of Semantics (1944). According to Tarski, we must distinguish between a formal language and its interpretation as applicable within a specific domain, in order to define the truth of propositions within the formal language in terms of their satisfaction by the external conditions that obtain. Tarski's logical papers were collected in A Decision Method for Elementary Algebra and Geometry (1948) and Logic, Semantics, Metamathematics (1956).

Recommended Reading: Alfred Tarski, Introduction to Logic and to the Methodology of Deductive Sciences, tr. by Olaf Helmer (Dover, 1995) and Alfred Tarski and the Vienna Circle: Austro--Polish Connections in Logical Empiricism, ed. by Jan Wolenski and Eckhart Kohler (Kluwer, 1998).

Also see John Perry, SEP on Tarski and his theory of truth, MMT, EB, and ELC.


Logical truth. A statement which is necessarily true because, by virtue of its logical form, it cannot be used to make a false assertion.

Example: "If neither John nor Betty is here, then John is not here."

Also see EB.

Tautology (Taut.)

A rule of replacement of the forms:

	p ≡ ( p ∨ p )

	p ≡ ( p • p )

Example: "Paul is tall." is equivalent to "Paul is tall and Paul is tall."

Although its ordinary-language use invariably seems pointless and redundant, this pattern of reasoning is a useful principle in the rigorous develoment of the propositional calculus.

Taylor, Harriet Hardy (1807-1858)

English philosopher. In The Enfranchisement of Women (1851) Taylor argued that the confinement of women to domestic pursuits was harmful to all human beings. She wrote eloquently on behalf of voting rights for women, equal opportunities in education and employment, and the abolition of restrictive laws governing marriage and divorce. Through her long and intimate association with John Stuart Mill, Taylor significantly contributed to the application of utilitarian principles to social and political issues.

Recommended Reading: The Complete Works of Harriet Taylor Mill, ed. by Jo Ellen Jacobs and Paula Harms Payne (Indiana, 1998) and Sexual Equality: A John Stuart Mill, Harriet Taylor Mill, and Helen Taylor Reader, ed. by Ann P. Robson and John M. Robson (Toronto, 1994).

Also see SEP.

τεχνη [technê]

Greek term for the art, craft, or skill involved in deliberately producing something (ποιησις [poiêsis]), by contrast with those things that merely derive from nature (φυσις [physis]) or chance (τυχη [tychê]). Both Plato and Aristotle distinguished its productive and practical components from more theoretical concerns.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967) and David Roochnik, Of Art and Wisdom: Plato's Understanding of Techne (Penn. State, 1999).

Also see SEP, Evelyn Barker, and PP.

teleological argument

An attempt to prove the existence of god based upon an observation of the regularity or beauty of the universe. As employed by Cicero, Aquinas, and Paley, the argument maintains that many aspects of the natural world exhibit an orderly and purposive character that would be most naturally explained by reference to the intentional design of an intelligent creator. Hume pointed out that since we have no experience of universe-formation generally, supposed inferences to its cause are unwarranted. Moreover, Darwin's theory of natural selection offered an alternative, non-teleological account of biological adaptations. In addition, anyone who accepts this line of argument but acknowledges the presence of imperfection in the natural order is faced with the problem of evil. Nevertheless, reasoning of this sort remains a popular pastime among convinced theists.

Recommended Reading: Thomas St. Aquinas, , tr. by Anton C. Pegis (Notre Dame, 1997); William Paley, Natural Theology: Evidences of the Existence and Attributes of the Deity (Classworks, 1986); David Hume, Principal Writings on Religion, Including 'Dialogues Concerning Natural Religion' and 'Natural History of Religion', ed. by J. C. A. Gaskin (Oxford, 1998); and Delvin Lee Ratzsch, Nature, Design, and Science: The Status of Design in Natural Science (SUNY, 2001).

Also see SEP and EB.

τελος [télos]

Greek term for the end, completion, purpose, or goal of any thing or activity. According to Aristotle, this is the final cause which accounts for the existence and nature of a thing. Following Wolff, modern philosophers (often pejoratively) designate as teleological any explanation, theory, or argument that emphasizes purpose.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967); F. M. J. Waanders, History of Telos and Teleo in Ancient Greek (Benjamins, 1984); Immanuel Kant, Critique of Judgment, tr. by Werner S. Pluhar (Hackett, 1987); William J. Fitzpatrick, Teleology and the Norms of Nature (Garland, 2000); Rowland Stout, Things That Happen Because They Should: A Teleological Approach to Action (Oxford, 1996); and Ernest Nagel, Teleology Revisited (Columbia, 1982).

Also see SEP, EB, and PP.

Teresa of Ávila (Teresa Sánchez de Cepeda y Ahumada) (1515-1582)

Spanish mystic. Teresa's The Way of Perfection (1566) and The Interior Castle sharply distinguished intellectual from volitional portions of human nature and recommended the total surrender of the soul to god through both prayerful meditation and ecstatic union with the divine.

Recommended Reading: The Life of Saint Teresa of Avila by Herself, tr. by J.M. Cohen (Penguin, 1988); Rowan Williams, Teresa of Avila (Continuum, 2000); and Cathleen Medwick, Teresa of Avila: The Progress of a Soul (Doubleday, 2001).

Also see EB and James E. Kiefer.

terminus a quo / terminus ad quem

Latin phrases for "limit from which" and "limit to which;" hence, the temporal starting-point and ending-point for the occurrence of any event, the moments of its beginning and its completion.

Thales (c. 585 BCE)

Presocratic philosopher who first proposed rational explanation of the natural world. In fragmentary reports from other philosophers, Thales is supposed to have held that "All is water." His Milesian followers commonly disagreed with this simple identification of the αρχη [archê].

Recommended Reading: G. S. Kirk and J. E. Raven, The Presocratic Philosophers: A Critical History With a Selection of Texts (Cambridge, 1988); Jonathan Barnes, The Presocratic Philosophers (Routledge, 1982); and The Cambridge Companion to Early Greek Philosophy, ed. by A. A. Long (Cambridge, 1999).

Also see IEP, John Burnet, EB, Ralph Nicholas Wedgewood, MMT, ELC, and WSB.


Belief in the existence of god as a perfect being deserving of worship.

Recommended Reading: Richard Swinburne, The Coherence of Theism (Clarendon, 1993); J. J. C. Smart and J. J. Haldane, Atheism and Theism (Blackwell, 1996); Alvin Plantinga, God and Other Minds: A Study of the Rational Justification of Belief in God (Cornell, 1990); Richard Swinburne, The Existence of God (Clarendon, 1991); and Stephen T. Davis, God, Reason, and Theistic Proofs (Eerdmans, 1997).

Also see ISM, Richard Swinburne, and EB.


An attempt to explain or defend the perfect benevolence of god despite the apparent presence of evil in the world. In this vein, for example, Leibniz devoted great effort to demonstrating that this is the best of all possible worlds.

Recommended Reading: Gottfried Wilhelm Leibniz, Theodicy: Essays on the Goodness of God, the Freedom of Man, and the Origin of Evil, ed. by Austin Marsden Farrer (Open Court, 1988); The Problem of Evil: A Reader, ed. by Mark Larrimore (Blackwell, 2000); Susan Neiman, Evil in Modern Thought: An Alternative History of Philosophy (Princeton, 2002); Richard Swinburne, Providence and the Problem of Evil (Oxford, 1998); and Alvin Plantinga, God, Freedom, and Evil (Eerdmans, 1978).

Also see SEP, EB, and CE.

theoretical definition

A proposal for understanding the meaning of a term in relation to a set of scientificaly useful hypotheses.

thesis / antithesis / synthesis

In the philosophy of Hegel, the inevitable transition of thought, by contradiction and reconciliation, from an initial conviction to its opposite and then to a new, higher conception that involves but transcends both of them. Thus, for example:

Being / Non-being / Becoming,

subjective / objective / absolute, or

symbolic / classical / romantic.

Since he identified reality with thought, Hegel believed that the same triadic movement is to be found in nature, cultural progress, and history.

Recommended Reading: Hegel's Science of Logic, tr. by A. V. Miller (Humanity, 1998); Quentin Lauer, Essays in Hegelian Dialectic (Fordham, 1977); and Hans-Georg Gadamer, Hegel's Dialectic, tr. by P. Christopher Smith (Yale, 1982).

thing-in-itself {Ger. Ding an sich}

An object as it is (or would be) independently of our awareness of it; the noumenon. As Kant showed, we cannot know things-in-themselves but can only postulate their nature from what we know about observable phenomena.

Recommended Reading: Immanuel Kant, Critique of Pure Reason, tr. by Werner S. Pluhar and Patricia Kitcher (Hackett, 1996); Sebastian Gardner, Routledge Philosophy Guidebook to Kant and the Critique of Pure Reason (Routledge, 1999); Gerold Prauss, Kant und das Problem der Dinge an sich; and Rae Langton, Kantian Humility: Our Ignorance of Things in Themselves (Clarendon, 1998).

Also see and Stephen Palmquist.

Thomas Aquinas

Italian Dominican philosopher and theologian.

For a discussion of his life and works, see Aquinas.

Thomson, Judith Jarvis (1929- )

American moral philosopher; author of Acts and Other Events (1977), The Realm of Rights (1990), and Moral Realtivism and Moral Objectivity (1996). In Rights, Restitution, and Risk: Essays in Moral Theory (1986) Thomson develops an ethical stance grounded upon the defeasible presumption of individual rights. Thomson's A Defence of Abortion (1971) famously establishes that termination of pregnancy, under certain circumstances, is morally permissible even if the fetus is granted status as a person entitled to rights. Abortion (1995) offers her more recent reflections on the same subject.

Recommended Reading: Fact and Value: Essays on Ethics and Metaphysics for Judith Jarvis Thomson, ed. by Alex Byrne, Robert Stalnaker, and Ralph Wedgwood (MIT, 2001).

Also see Stephen Darwall and Frank Bouchier-Hayes.

Thoreau, Henry David (1817-1862)

American writer. Thoreau's essay "On Civil Disobedience" (1849) is a classic statement of the principles, later employed by Gandhi and King, of passive resistance against governmental authority on the basis of individual conscience. Thoreau's Walden, or Life in the Woods (1854) describes and recommends a spontaneous life of creativity in purposeful union with the natural world.

Recommended Reading: The Portable Thoreau, ed. by Carl Bode (Viking, 1977) and Robert D. Richardson, Jr. and Barry Moser, Henry Thoreau: A Life of the Mind (California, 1988).

Also see The Thoreau Reader, SEP, The Thoreau Society, EB, ELC, and Philip Cafaro.


Creative Commons License
The Philosophy Pages by Garth Kemerling are licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Permissions beyond the scope of this license may be available at

©1997, 2011 Garth Kemerling.
Last modified 31 December 2011.
Questions, comments, and suggestions may be sent to: the Contact Page.