Sufficient reason, principle of

From New World Encyclopedia

The principle of sufficient reason is the principle which is presupposed in philosophical arguments in general, which states that anything that happens does so for a definite reason. It is usually attributed to Gottfried Leibniz. Leibniz formulated the principle as follows: "There must be a sufficient reason [often known only to God] for anything to exist, for any event to occur, for any truth to obtain."[1]


The principle has a variety of expressions, all of which are perhaps best summarized by the following:

  • For every entity x, if x exists, then there is a sufficient explanation why x exists.
  • For every event e, if e occurs, then there is a sufficient explanation why e occurs.
  • For every proposition p, if p is true, then there is a sufficient explanation why p is true.

A sufficient explanation may be understood either in terms of reasons or causes for like many philosophers of the period, Leibniz did not carefully distinguish between the two. The resulting principle is very different, however, depending on which interpretation is given.

Leibniz's view

In fact Leibniz opposed fatalism and had a more nuanced and characteristic version of the principle, in which the contingent was admitted on the basis of an infinite number of reasons, to which God had access but humans did not. He explained this while discussing the problem of the future contingents:

We have said that the concept of an individual substance (Leibniz also uses the term haecceity) includes once for all everything which can ever happen to it and that in considering this concept one will be able to see everything which can truly be said concerning the individual, just as we are able to see in the nature of a circle all the properties which can be derived from it. But does it not seem that in this way the difference between contingent and necessary truths will be destroyed, that there will be no place for human liberty, and that an absolute fatality will rule as well over all our actions as over all the rest of the events of the world? To this I reply that a distinction must be made between that which is certain and that which is necessary. (§13, Discourse on Metaphysics. Retrieved February 19, 2008.)

Without this qualification, the principle can be seen as a description of a certain notion of closed system, in which there is no 'outside' to provide unexplained events with causes. It is also in tension with the paradox of Buridan's ass.

As a Law of Thought

The laws of thought are fundamental logical rules, with a long tradition in the history of philosophy, which collectively prescribe how a rational mind must think. To break any of the laws of thought (for example, to contradict oneself) is to be irrational.

Leibniz counted the principle of sufficient reason together with the principle of the identity of indiscernibles to a list of the most general logical principles discussed since Aristotle.


The three classic laws of thought are attributed to Aristotle and were foundational in scholastic logic. They are:

  • law of identity
  • law of noncontradiction
  • law of excluded middle


John Locke claimed that the principles of identity and contradiction were general ideas and only occurred to people after considerable abstract, philosophical thought. He characterized the principle of identity as "Whatsoever is, is." The principle of contradiction was stated as "It is impossible for the same thing to be and not to be." To Locke, these were not innate or a priori principles.


Leibniz formulated two additional principles, either or both of which may sometimes be counted as a law of thought:

In Leibniz's thought and generally in the approach of rationalism, the latter two principles are regarded as clear and incontestable axioms. They were widely recognized in European thought of the seventeenth, eighteenth, and (while subject to greater debate) nineteenth century. As turned out to be the case with another such (the so-called law of continuity), they involve matters which, in contemporary terms, are subject to much debate and analysis (respectively on determinism and extensionality). Leibniz's principles were particularly influential in German thought. In France the Port-Royal Logic was less swayed by them. Hegel quarrelled with the identity of indiscernibles in his Science of Logic (1812-1816).

Schopenhauer's On the Fourfold Root of the Principle of Sufficient Reason

On the Fourfold Root of the Principle of Sufficient Reason[2] was originally published as a doctoral dissertation in 1813. The German philosopher Arthur Schopenhauer revised this important work and re-published it in 1847. Throughout all Schopenhauer's later works he consistently refers his readers to this short treatise as the necessary beginning point for a full understanding of his entire system.



In January of 1813, after suffering their disastrous defeat in Russia, the first remnants of Napoleon's Grand Armée was arriving in Berlin. The sick and wounded quickly filled up the hospitals and the risk of an epidemic grew high. A patriotic, militaristic spirit inflamed the city and most of the populace, philosophers and students included, entertained the hope that the French yoke could be violently thrown off. All this rapidly became intolerable to Schopenhauer who ultimately fled the city, retreating to the small town of Rudolstadt near Weimar. It was here, from June to November of that year, while staying at an inn, that the work was composed.

After submitting it as his doctoral dissertation he was awarded a PhD from the University of Jena in absentia. Private publication soon followed. "There were three reviews of it, commending it condescendingly. Scarcely more than one hundred copies were sold, the rest was remaindered and, a few years later, pulped.”[3] Among the reasons for the cold reception of this original version is that it lacked the author's later authoritative style and appeared decidedly unclear in it's implications. A copy was sent to Goethe who responded by inviting the author to his home on a regular basis, ostensibly to discuss philosophy but in reality to recruit the young philosopher into work on his theory of colours.

In 1847 Schopenhauer rewrote and enlarged the work, publishing a new edition. This is the version of the work that is read today. "There the lines of thought are firmly pursued, linking up with his main work; there a challenge is issued to philosophical tradition, and there is no curb on attacks against the philosophical spirit of the age.”[4]


Schopenhauer’s epistemology, by direct admission, begins with Immanuel Kant's theory of knowledge. Actually, Schopenhauer proclaimed himself a Kantian who had appropriated his predecessor's most powerful accomplishment in epistemology, and who then claimed to have merely extended and completed what Kant botched or had left undone.

In Schopenhauer’s point of view, Kant’s chief merit lies in his distinction between the thing in itself and the phenomenal world in which it appears, i.e., the world as we represent it to ourselves. What is crucial here is the realization that what makes experience possible to begin with and without exception is our perceiving mind, which synthesizes perceptions from raw sensation and consequently abstracts concepts from those perceptions. Schopenhauer appropriates Kant’s forms of sensibility (space, time, and causality) and transforms them into what he calls the understanding:

"To know causality is the sole function of the understanding, its only power, and it is a great power embracing much, manifold in its application, and yet unmistakable in its identity throughout all its manifestations. Conversely, all causality, hence all matter, and consequently the whole of reality, is only for the understanding, through the understanding, in the understanding. The first, simplest, ever-present manifestation of understanding is perception of the actual world. This is in every way knowledge of the cause from the effect, and therefore all perception is intellectual" (The World as Will and Representation volume I 11).

Thus, understanding does not exist independent of our ability to perceive and determine relationships as it is the very ground of experience itself. Not only what we think in the abstract, but also our very perceptions are completely intellectual and subjectively determined. Already we have the philosophical grounds for Nietzsche’s perspectivism, though given in different language: representation (Vorstellung).

On the Fourfold Root of the Principle of Sufficient Reason

According to Schopenhauer's On the Fourfold Root of the Principle of Sufficient Reason, there are four distinct forms of the principle.

  • Principle of Sufficient Reason of Becoming

If a new state of one or several real objects appears, another state must have preceded it upon which the new state follows regularly.

  • Principle of Sufficient Reason of Knowing

If a judgment is to express a piece of knowledge, it must have a sufficient ground. By virtue of this quality, it receives the predicate true. Truth is therefore the reference of a judgment to something different there from.

  • Principle of Sufficient Reason of Being

The position of every object in space and the succession of every object in time is conditioned by another object's position in space and succession in time.

  • Principle of Sufficient Reason of Acting

Every human decision is the result of an object that necessarily determines the human's will by functioning as a motive.

See also

  • deterministic system (philosophy)
  • Law of thought


  1. There are numerous anticipations. One often pointed to is in Anselm of Canterbury: his phrase quia Deus nihil sine ratione facit Cur Deus homo and the formulation of the ontological argument for the existence of God. A clearer connection is with the cosmological argument for the existence of God. The principle can be seen in both Thomas Aquinas and William of Ockham. Leibniz formulated it, but was not an originator. See chapter on Leibniz and Spinoza in A. O. Lovejoy, The Great Chain of Being. Retrieved February 19, 2008.
  2. In German, Über die vierfache Wurzel des Satzes vom zureichenden Grunde
  3. Safranski, 156
  4. Safranski, 157

ISBN links support NWE through referral fees

  • Aristotle. "On Interpretation." in Aristotle, Vol. 1, Harold P. Cooke (trans.). Loeb Classical Library, 111-179 (London, UK: William Heinemann, 1938).
  • Aristotle. "Prior Analytics." in Aristotle, Vol. 1, Hugh Tredennick (trans.). Loeb Classical Library, 181-531 (London, UK: William Heinemann, 1938).
  • Aristotle. "The Categories." in Aristotle, Vol. 1, Harold P. Cooke (trans.). Loeb Classical Library, 1-109 (London, UK: William Heinemann, 1938).
  • Aristotle, and Richard Peter McKeon. The Basic Works of Aristotle. New York: Random House, 1941.
  • Schopenhauer, Arthur. The World as Will and Representation, Volume 2. New York: Dover Publications, 1966. ISBN 0-486-21762-0
  • Boole, George. An Investigation of the Laws of Thought on Which are Founded the Mathematical Theories of Logic and Probabilities. Macmillan, 1854. Reprinted with corrections, New York: Dover Publications, 1958.
  • Gurr, John Edwin. The Principle of Sufficient Reason in Some Scholastic Systems, 1750-1900. Marquette University Press, 1959.
  • Leftow, Brian. "On a Principle of Sufficient Reason." in Religious Studies, 2003, 39, no. 3: 269-286.
  • Lovejoy, Arthur O. The Great Chain of Being; A Study of the History of an Idea. Cambridge, Mass: Harvard University Press, 1936.
  • Pruss, Alexander R. The Principle of Sufficient Reason A Reassessment. Cambridge studies in philosophy. New York: Cambridge University Press, 2006. ISBN 052185959X
  • Russell, Bertrand. The Problems of Philosophy. London: Williams and Norgate, 1912.
  • Safranski, Rüdiger. Schopenhauer and the Wild Years of Philosophy. Harvard University Press, 1990. ISBN 0-674-79275-0

External links

All links retrieved February 26, 2023.

General Philosophy Sources


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