# irrational

As irrational (from Latin : irrationalis , "unreasonable") one designates facts or ideas that contradict or evade human reason (Latin: ratio ). The term irrationality is sometimes used synonymously as a substantiated adjective for the irrational , sometimes it denotes the human characteristic of unreason .

In mathematics , a number isirrational ” if it cannot be represented as a finite or periodic decimal number ( rational number ), so it can never be (completely) calculated or specified as a decimal number. These are those real numbers that cannot be expressed as a fraction of two whole numbers , such as or the circle number π. ${\ displaystyle {\ sqrt {2}}}$

## Definition

In everyday parlance, the term is used in different meanings. To call a state of affairs “irrational” can mean that it may exist but is inaccessible to the mind . H. cannot be rationally explained. But it can also mean that he, because he rational criteria contradicts (about the principle of consistency , per se do not exist) can . The term “ir-rational” must also be differentiated from the psychological term of the unconscious , i.e. contents which are either only not conscious at a certain time or which, like some brain processes, never run consciously, but which do not contradict reason directly .

Furthermore, it should be noted that every reflection, every belief in, every thinking about the irrational can only take place within a certain conceptual discourse and is fundamentally subject to the logical rules of language and reason. The use of the term “ir-rational” itself always presupposes the rational, to which the ir-rational is negatively related.

## Concept history

The concept of irrationality comes from mathematics and was first used philosophically by the Jewish philosopher Salomon Maimon in his attempt on the transcendental philosophy (1790). Obviously, this work was a reaction to the previously published Critique of Pure Reason (1781) by Immanuel Kant . The concept of irrationality then found its way into the philosophy of German idealism : In a letter from Johann Gottlieb Fichte to Friedrich Wilhelm Joseph Schelling from 1801, in a letter to Friedrich Heinrich Jacobi from 1804, and in the Wissenschaftslehre from 1804 , Fichte speaks of the “proiectio per hiatum irrational ". In his lectures on the philosophy of art in 1802/1803, Schelling used the term irrational in that he presented art as a higher form of reason which was irrational for the analytical mind. Soon, the concept of the irrational is also in the aesthetics of Friedrich Schleiermacher and Georg Wilhelm Friedrich Hegel in his Science of Logic . In his teaching on analytical psychology, CG Jung differentiates between rational ( thinking and feeling ) and irrational psychological functions ( intuition and feeling ), cf. → Positive philosophy .

In the 19th century, Fyodor Dostoyevsky did a great job of rehabilitating the irrational, which a few decades later led to the foundation of psychoanalysis .