Rationalism as a philosophy stresses reason as the means of determining truth. Mind is given authority over sense, the _w:a priori over the w:a posteriori_. Rationalists are usually foundationalists, who affirm that there are first principles of knowledge, without which no knowledge is possible. For a rationalist, reason arbitrates truth, and truth is objective.

Although w:Aristotle (384-322 B.C.) believed that knowledge began in the senses, his stress on reason and logic made him the father of Western rationalism. w:René Descartes (1596-1650), w:Benedict Spinoza (1632-1677), and w:Gottfried Leibniz (1646-1716) were the chief modern rationalists.^[1]^ ^ [2]^ ^[3]^

Most worldviews have at least one major rationalist proponent. Leibniz embraced theism.^[4]^ Spinoza held to pantheism.^[5]^ w:Ayn Rand (1905-1977) professed atheism.^[6]^ Most deists held some form of rationalism. Even pantheism is represented by strong rationalistic proponents, such as w:Charles Hartshorne (1897-2000).^ [7]^ Finite godism has been rationally defended by w:John Stuart Mill (1806-1873) and others.^[8]^

The reason that various worldviews all have forms of rationalism is that rationalism is an epistemology, whereas a worldview is an aspect of metaphysics. Rationalism is a means of discerning truth, and most worldviews have exponents who use it to determine and defend truth as they see it.^[9]^

Central Premises

Premises Shared by Rationalists

Some ideas are common to virtually all rationalists. These include the following factors, even though some rationlists defend them, modify them, or limit them in ways others do not.

  • Foundationalism. Foundationalism believes that there are first principles of all knowledge, such as the principle of noncontradiction, the principle of identity, and the principle of the excluded middle. Certain foundationalists believer there are other principles, either the principle of sufficient reason or the principle of causality. All rationalists are foundationalists, and all foundationalists believe in some foundational principles.
  • Objectivism. Rationalists also believe that there is an objective reality and that it can be known by human reason. This distinguishes them from mysticism, existentialism, and other forms of subjectivism. For a rationalist, the real is rational, and reason is the means of determining what is real.
  • Exclusivism. Rationalists are also exclusivists. They believe that mutually exclusive opposites cannot both be true. According to the law of non-contradiction, if atheism is true, then all non-atheism is false. If Christianity is true, then all non-Christian systems are false. But opposite truth claims cannot both be true.
  • A Priorism. All rationalists believe there is an a priori element to knowledge. Reason is in some sense independent of experience. Even rationalists who are also empiricists (i.e. Thomas Aquinas, w:Aristotle, and w:Leibniz), believe that there is nothing in the mind that was not first in the senses except the mind itself. Without this a priori (independent of experience) dimension to knowledge, nothing could be known.^ [10]^

Differences Among Rationalists

The Role of the Senses

Some rationalists downplay, if not negate, any determinative role of the senses in the knowing process. They stress the rational exclusively. w:Spinoza is an example of this view. Others combine sense and reason, such as Aquinas and w:Leibniz. The former are more deductive in their approach to learning truth; the latter are more inductive and inferential.

The Limits of Reason

A crucial difference among rationalists is found in the scope of reason. Some rationalists, such as w:Spinoza, give reason an all-encompassing scope. It is the sole means of determining truth. Others, such as Aquinas, believe reason is capable of discovering some truths (i.e. the existence of God), but not all truth (i.e. the Trinity).^[11]^ Those in the latter category believe that there are truths that are in accord with reason and some that go beyond reason. Even the latter are not contrary to reason. They simply are beyond the ability of reason to attain on its own. They can be known only from special revelation.


Rationalism as a whole has both positive and negative dimensions for an apologists. Unlimited rationalism that denies all special revelation, obviously is unacceptable for a theist. Nor is any form of rationalism that denies theism in accord with orthodox Christianity.

However, foundationalism's stress on the need for first principles, is both true and valuable. Also valuable is the belief in objective truth. The rationalist's emphasis on the exclusive nature of truth claims is also a benefit to Christian apologetics.

From a Christian perspective, the rationalist theologian Jonathan Edwards made an important distinction: All truth is given by revelation, either general or special, and it must be received by reason. Reason is the God-given means for discovering the truth that God discloses, whether in his world or his Word. While God wants to reach the heart with truth, he does not bypass the mind along the way.^ [12]^ In this modified sense, there is great value in Christian rationalism.


  1. ? René Descartes, Meditations, (New York: Liberal Arts, 1951).
  2. ? Benedictus de Spinoza, The Ethics of Spinoza: The Road to Inner Freedom, (Secaucus, N.J.: Citadel Press, 1976).
  3. ? Gottfried Wilhelm Leibniz, Discourse on Metaphysics, (Manchester: Manchester University Press, 1953).
  4. ? Leroy E. Loemker, Philosophical Papers and Letters, (Dordrecht, Holland: D. Reidel Pub. Co, 1976), 717.
  5. ? Correspondence of Benedict de Spinoza, Wilder Publications (March 26, 2009), ISBN-10:1604591560, letter 73.
  6. ? Chris Matthew Sciabarra, Ayn Rand: The Russian Radical, (University Park, Pennsylvania: Pennsylvania State University Press, 1995), 1.
  7. ? Charles Hartshorne, Man's Vision of God and the Logic of Theism, (Chicago: Willett, Clark & Co, 1941), 348.
  8. ? John Stuart Mill, Nature, the Utility of Religion, and Theism, (London: Longmans, Green, 1885).
  9. ? Norman L. Geisler and Winfried Corduan, Philosophy of Religion, (Grand Rapids: Baker, 1988).
  10. ? Ibid.
  11. ? Thomas Aquinas, Summae Theologiae, (London: Blackfriars, 1980).
  12. ? Jonathan Edwards, "The Mind" The Philosophy of Jonathan Edwards from His Private Notebooks, (Eugene: University of Oregon, 1955).