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The concept of reason in its modern use denotes a mental human capacity for knowledge that is determined by thinking . Based on the terminological use by Christian Wolff , it is separated from the mind , which records facts through observation and experience and gives it the function of developing generally valid connections through conclusions , recognizing their meaning and establishing rules and principles . If these concern actions , value determinations or questions of morality , one speaks of practical reason. In addition to the ability of the principles, this term also includes the ability to determine one's own will. The use related to knowledge and science is called theoretical reason. Rationality , in turn, is a concept of "reasonableness", which can be oriented towards increasing efficiency, both in the sense of economic viability according to economic principles and in the sense of the theory of justice or discourse ethics .

The content of the concept of reason is determined differently. In its relationship with the concept of understanding, it has experienced a change in the course of history from Greek philosophy - Nous and Logos versus dianoia - through the Middle Ages - intellectus versus ratio - to modern times . In the modern age, initiated by Meister Eckart and Luther , a conceptual content developed as it was formulated by Immanuel Kant in the Critique of Pure Reason and is thus still largely common in modern times. According to this, reason is the supreme faculty of knowledge . This controls the mind with which the perception is structured, recognizes its limitations and can set limits. This makes reason the essential means of spiritual reflection and the most important tool of philosophy . However, this understanding has also been criticized, for example by Arthur Schopenhauer , where reason is the organ of empty speculation and understanding is the actual, higher faculty of knowledge.

In addition to this reason as the subjective faculty of a person or "finite rational being" ( animal rationale ) - some philosophers assumed the existence of an objective reason: a principle that rules and regulates the world as metaphysical or cosmological reason - world reason, world spirit , logos , God . These philosophers include B. Heraclitus , Plotinus and Hegel . The debates about the existence or non-existence of such a world reason and its possible nature are an important part of the history of philosophy . For this purpose, Kant uses the concept of divine reason ( intellectus archetypus ) in his Critique of Practical Reason, which stands in contrast to human reason ( intellectus ectypus ).

In contrast to the concept of reason , the concept of understanding is used today for cases in which phenomena are considered separately, detached from the larger, comprehensive context. In everyday language , however, there is no strict distinction between the two terms.


Both colloquially and in the history of philosophy, the term “reason” has several meanings that overlap.

On the one hand, it is viewed as the basis for knowledge and gain in knowledge. It creates the prerequisite for knowledge by providing a system and a frame of reference for knowledge . The understanding is usually distinguished from reason as the faculty of knowledge or as the interaction of many different cognitive abilities.

On the other hand, reason is used to mean sensible action . In this sense, reason establishes a normative , philosophical ethic that does not admit any appeal to other authorities. It can be found, for example, in Aristotle as the right measure or in Immanuel Kant as the categorical imperative . In his Universal History Voltaire describes a steady development of humanity from primitive barbarism to the predominance of reason.

Finally, reason is used to mean "according to a higher order". This view mostly bears the traits of a religious conviction, and also in German idealism reason is the “thinking of God”. In idealism, man and all of humanity have a share in this reason, but it takes place in him rather than having an influence on it. Even without a traditional religious reference, many people today are convinced that they will encounter a higher reason of creation in the world (cf. Intelligent Design ). Physicists like Erwin Schrödinger were convinced of the existence of a supernatural , rational order.

History of philosophy


In Plato there is a distinction between noesis and dianoia . Noesis as the “intuitive seeing of ideas ” describes the ability to recognize beings in their essence , while dianoia means the conceptual, methodical - discursive way of knowledge.

Aristotle determined reason on two levels. On the one hand there is thinking reason, the logos, which is a conversation with itself, and on the other hand reason that guides action, the phronesis , which is directed towards practice. There is a direct relationship between phronesis and logos ( EN VI 5, 1140 b20). The logos determines reasonable action as it serves to grasp the mean of virtue (see mesotes ). Humans are not just a community ( zoon politikon ), but also a rational being ( zoon logon echon ) ( Pol . I 2, 1253 a1-18) As for Heraclitus or Anaxagoras , Aristotle the nous was a general, unchangeable world principle. “Anaxagoras is right when he describes the spirit (nous) as that which cannot be affected and is unmixed, precisely because he applies it as the principle (arché) of movement. Because only under this condition can he move as unmoved and rule as unmixed. "( Physik 5, 256 b24 f)

In the Stoa , reason served to regulate the physical instincts and thus lead to a balanced, virtuous life. Man is part of nature and the task of reason is to insert life into the cosmic order (logos). Reason cannot go against the order of nature. Cicero asks : "Is anything natural that happens against reason (ratio)?" ( Conversations in Tusculum , 4th book, 79 f.). In Seneca , the answer is: "namely you have to take nature for leaders: it observes the reason (ratio), and that she asks for help."

European Middle Ages

The Latin terminology translated noesis with intellectus and dianoia with ratio . The philosophy of the Middle Ages was shaped in its beginnings by the idea of ​​an integration of religion and philosophy. Both should not come into contradiction to one another. Augustine of Hippo was a major pioneer in this regard : “There are two different remedies that must be used in succession, namely authority and reason. Authority demands faith and prepares man for reason. Reason leads to insight and knowledge. But authority is not completely abandoned by reason either, since one has to consider whom one should believe, and the already evident and recognized truth is no less the undoubtedly supreme authority. "It is no longer nature, as in the Stoa, but a transcendent divine will, as in Neoplatonism , which is the standard for human action. “The first corruption of the rational soul is the will to do what the highest and innermost truth forbids. As a result, man was expelled from paradise into our earthly world and thus came from eternity into the temporal, from abundance into want, from strength into weakness, but not from essentially good to essentially bad. Because no being is bad. "

In the Middle Ages , however, God was also thought of as an authority that takes precedence over all human thinking, with Petrus Damiani even going so far that thinking has its origin in the devil and is nothing before God. Accordingly, he took the view that philosophy was the " handmaid of theology ".

Thomas Aquinas , on the other hand, considered it necessary that the knowledge of the world should not be based on errors, because this endangers correct belief in God. “So it is obvious that the opinion of certain people is wrong, who say that the truth of faith does not depend on what one thinks about creatures, if one only has the right opinion about God [...] because the error about the creatures turns into a wrong opinion of God and leads the spirit of men away from God, to which faith tries to direct them by the error subordinating the creatures to other causes. "( ScG II 3 No. 864) . For Thomas, action that yields to unreasonable urges is bad. "Any willingness that deviates from reason, whether right or wrong, is always bad." ( STh I / II 19 a.5)

In high scholasticism , the striving to separate beliefs and reason developed again. Important representatives of this development were Johannes Duns Scotus and Wilhelm von Ockham . In Meister Eckhart and Martin Luther intellectus was again equated with understanding and ratio with reason, whereby the understanding (intellectus / noesis) as the essential knowledge of the discursive and argumentative operating reason (ratio / dianoia) was superior.

Non-European philosophy

Similar approaches can be found in almost all cultures. In the Islamic tradition, the influential philosopher Avicenna described reason as a steady emanation of God. Eastern wisdom teachings like yoga and zen teach the limits and contradictions of reason and how one can free oneself from them.

Nikolaus von Kues

Nikolaus von Kues emphasized that reason is a special human ability that can only develop its strength through education. “As humans, humans relate to animals as an educated person relates to an untrained one. The learned sees the letters of the alphabet ( litteras alphabeti ) and so does the unlearned. However, the instructed forms syllables ( syllabas ) and syllables from syllables and from these sentences by various combinations of letters . The unlearned cannot do this because he lacks the art that the instructed has acquired through training his reason ( ab exercitato intellectu ). Through the power of his reason, man is able to put together and separate the natural cognitive images ( species naturales ) and to create cognitive images and cognitive signs of reason and art from them. In this way, the human being towers over the animals and the instructed over the unlearned because he has a trained and educated reason ( exercitatum et reformatum intellectum ). "

With Cusanus, as later with Kant, reason is the highest level in the triad of sense - understanding - reason. While the understanding summarizes the various sensory impressions, the insight of reason in the view of the higher goes beyond the understanding. The unity of reason itself as the simplest synopsis of the whole, he described, following Raimundus Llullus, as a triad of (1) what knows , (2) what is known and (3) the process of knowing. The intellect exceeds the ratio insofar as it forms a unity from what is discursively separated in the ratio ( intelligens, intelligibile, intelligere ). This triad of (1) undividedness ( indivisio ), (2) differentiation ( discretio ) and (3) compound ( conexio ) refers to the theory of categories at Charles S. Peirce and the process philosophy in Whitehead , in the category of the elemental (see Process and reality ). The unity of reason is the coincidence of opposites ( Coincidentia oppositorum ). Like understanding, reason is also limited. The essence of God as light that comes to meet her remains closed to her. “Hence reason moves towards wisdom as its very life. And it is sweet for every spirit to constantly ascend to the origin of life, even though it is inaccessible. [...] As if someone loves something because it is lovable, he is happy that in what is lovable there are infinite and inexpressible reasons for love. "


The European Age of Enlightenment is based on the idea that reason is able to bring the truth to light. The religion of reason should overcome the dogmatic oppression and the belief in authority of the Christian religion and bring freedom and prosperity for all. Thus rationalism saw in reason the "pure", i. H. cognition independent of empirical experience, which in Descartes , Spinoza and Leibniz formed the basis of philosophical systems. The concept of human reason has often been equated with consciousness , self- awareness , or spirit . In rationalism, reason represents the central element of the cognitive process. With it, deductive cognitions are possible, which can also be achieved without sensory perceptions. In contrast, there is empiricism (e.g. David Hume ), which offers a priori possibility of knowledge , i.e. H. denies without experience.


At the end of the 18th century, Immanuel Kant brought the approaches of rationalism and empiricism together in his critical philosophy . With Kant, reason finally gained its importance as the higher principle of knowledge than understanding. He defined the understanding as the cognitive faculty that is bound to sensory impressions and working a posteriori . In terms of reason, he distinguished between (“pure”) theoretical and practical reason. According to Kant, theoretical reason is the ability to draw conclusions, to examine oneself and to arrive at the a priori rational ideas ( soul , God , world ) independently of experience . In his work Critique of Pure Reason , Kant tries above all to point out the limits and the condition of human reason. This could free the concept of reason from metaphysical speculations and pave the way for scientific metaphysics . Kant thus contributed significantly to the most important methods practiced today in science , in which theoretic development and the empirical experiment are carried out reciprocally. Practical reason, on the other hand, according to Kant, refers to the setting of ethical principles to which the will is subjected and which thus justify and guide action individually and socially. At the beginning of the preface to the 1st edition of the Critique of Pure Reason it says:

“Human reason has a special fate in one species of its knowledge: that it is troubled by questions that it cannot reject; for they are given to it by the nature of reason itself, which it cannot answer either; because they exceed all capabilities of human reason. "

- Immanuel Kant


After Kant had described the limits of knowledge and reason, some representatives of German idealism refused to accept them. Hegel expressly recognizes Kant's insight into reason as the ground (substance) of freedom. But he describes Kant's position as subjective because he only allows the subject to recognize true appearances of things and not these themselves as they are in themselves. To go beyond that, you need absolute reason . With him it is the speculative ability to grasp the absolute in the movement of all its moments. For him it is the ground that creates unity and meaning that goes out of itself forever, divides itself in such a way that it is realized (or materialized) again in the course of history in ever new appearances as (time) spirit and nature the unity falls and so "returns to (or in) itself". Hegel says that because it takes everything back into itself and brings it into its form (the unity), i.e. basically has no limit, it is infinite, and because it only knows itself, it is absolute . For him the absolute itself is God, the absolute spirit. For Hegel, to recognize him is the ultimate goal of all philosophy. The connection of reason with the historical process has subsequently developed a very clear effect, particularly through Marxism . Reason and progress (economic, scientific, technical, social) have since been closely linked in their social significance. In contrast, the idea of ​​freedom of reason from the Enlightenment was largely suppressed.


Arthur Schopenhauer differentiates understanding as the ability for vivid recognition and reason as that for abstract, discursive recognition. He regards reason as specifically human, whereas understanding also belongs to (higher) animals. Some of these are even able to understand multilevel causal relationships, but they cannot think rationally because they lack abstract concepts and ideas.


In view of the horrors of the 20th century ( Holocaust , imperialism ), which they also saw as being related to industrialization , the members of the Frankfurt School developed a critique of rationality . She criticizes the modern scientific community and its factual belief , which is determined by positivism . Reason and understanding have become an instrument of the oppression of the individual and have almost stifled the “powers of self-liberation” of reason. Jürgen Habermas contrasts the “ instrumental reason ” ( Theodor W. Adorno , Max Horkheimer ) with the intersubjective “communicative reason” of the lifeworld, which is based on freedom from domination and violence and mutual recognition. A new level of enlightenment is necessary, which - according to Habermas - has not yet been completed.

In his thirteenth encyclical Fides et ratio in 1998, Pope John Paul II addressed the area of ​​tension between reason and faith from the point of view of the Roman Catholic Church. Pope Benedict XVI took up the thoughts of his predecessor in his speech at the University of Regensburg on September 12, 2006 and in his remarks on the Catholic Church's image of God.


In the neurosciences , mind is defined as fluid intelligence , i. H. the ability to think logically and solve problems . The neuronal structures responsible for this are located in the dorsolateral prefrontal cortex (DLPFC). If this part of the brain is injured, the affected patients behave "unintelligent" (e.g. remain stubborn with one behavior, although the situation has changed significantly). Under reason the necessary "reasonable behavior" skills are understood u. a. the assessment of factual and social consequences of action, the setting of action goals based on experience and the control of selfish behavioral impulses. The corresponding structures are mainly located in the orbitofrontal cortex (OFC). People with injuries in these areas show more “unreasonable” behavior (e.g. take great risks against their better judgment).


Anthologies and edited volumes

  • Karl-Otto Apel and Matthias Kettner (eds.): The one reason and the many rationalities . Suhrkamp, ​​Frankfurt 1996, ISBN 3-518-28807-5 .
  • Jose Luis Bermudez, Alan Millar (Eds.): Reason and Nature. Essays in the Theory of Rationality. Clarendon Press, Oxford 2002.
  • Paul K. Moser (Ed.): Rationality in Action. UK: Cambridge University Press, Cambridge 1990.
  • Hans Poser (ed.): Change of the concept of reason . Alber, Freiburg / Munich 1981, ISBN 3-495-47468-4 .

Overview of the history of philosophy

More specific literature

Web links

Wiktionary: Reason  - explanations of meanings, word origins, synonyms, translations
Wikiquote: Reason  - Quotes

Individual evidence

  1. ^ Friederike Rese: Practice and Logos in Aristotle: Action, Reason and Speech in Nicomachean Ethics, Rhetoric and Politics. Mohr Siebeck, Tübingen 2003, p. 2.
  2. ^ Friederike Rese: Practice and Logos in Aristotle: Action, Reason and Speech in Nicomachean Ethics, Rhetoric and Politics. Mohr Siebeck, Tübingen 2003, p. 21.
  3. Seneca: About the happy life . VIII, 1 )
  4. Augustine: About true religion. 24, 45, Reclam, Stuttgart 2006, pp. 122-123.
  5. Augustine: About true religion. 20, 38, Reclam, Stuttgart 2006, pp. 101-102.
  6. Petrus Damiani: De sancta simplicitate scientiae inflanti anteponenda, in: Jacques Paul Migne : Patrologia Latina PL Volume 145, 695–704, here 695
  7. Nikolaus von Kues: Compendium - Brief description of the philosophical-theological teachings. VI n, 18, quoted from: Rudi Ott: The human reason and the three God in Nikolaus von Kues: Explanations of the work De docta ignorantia - The instructed ignorance. Book I, Books on Demand, Norderstedt 2009, ISBN 978-3837084849 , p. 9.
  8. Nikolaus von Kues: De beryllo - About the beryl, n 12
  9. Rudi Ott: The human reason and the three gods in Nikolaus von Kues: Explanations of the work De docta ignorantia - The learned ignorance. Book I, Books on Demand, Norderstedt 2009, p. 86.
  10. Nikolaus von Kues: Idiota de sapientia - The layman about wisdom. I n 11, quoted from Rudi Ott: The human reason and the three-one God in Nikolaus von Kues: Explanations of the work De docta ignorantia - The learned ignorance. Book I, Books on Demand, Norderstedt 2009, p. 53.
  11. ^ Project Gutenberg
  12. HWPh Vol. 11, p. 834.
  13. ^ Vatican Radio - message from September 23, 2006 ; Faith, Reason and University (text of the lecture)
  14. Gerhard Roth : Personality, Decision and Behavior . Klett-Cotta , Stuttgart 2007, ISBN 978-3-608-94490-7 .