Tetens, Johann Nicolaus (1736 or 1738–1807)

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(1736 or 17381807)

Johann Nicolaus Tetens, the German philosopher and psychologist, was born in Tetenbüll, Schleswig, in 1736 or in Tönnig, Schleswig, in 1738, and died in 1807. He studied at the universities of Rostock and Copenhagen and became a Magister at Rostock University in 1759. From 1760 until 1765, when he became director of the local Gymnasium, he taught physics at Bützow Academy. He was full professor of philosophy at the University of Kiel from 1776 to 1789, during which period he also carried out an official study of the local hydraulic installations on the North Sea coast. From 1789 until his death he had a brilliant career as a high financial official in Copenhagen.

Tetens was strongly influenced by J. C. Eschenbach, his teacher of philosophy at Rostock. Eschenbach was an eclectic who accepted some Leibnizian and Wolffian tenets but sided with the Pietists against Christian Wolff; nevertheless, he seems to have been influenced more by the Berlin Academy and by John Locke's empiricism than by C. A. Crusius. Tetens likewise was influenced by Locke and, after their publication, by Gottfried Wilhelm Leibniz's Nouveaux Essais. Among his contemporaries he was influenced by David Hartley, Abraham Tucker, J. G. Sulzer, Claude-Adrien Helvétius, and Charles Bonnet. Tetens was one of the first in Germany to discuss David Hume at length. J. H. Lambert's Architektonik and Immanuel Kant's Inaugural Dissertation later played important roles in the development of Tetens's own views.

Tetens hoped to reform German metaphysics by using the critical approach of the new empirical psychology. He wished to restore metaphysics in a new form that would meet the criticisms based on the skeptical and psychological orientations of the English and French schools, then widely influential in Germany. On the other hand he defended phenomenalism against the adherents of the schools of common sense and of "popular philosophy."

In his first significant work, Ueber die allgemeine spekulativische Philosophie (On general speculative philosophy; Bützow and Wismar, 1775; reprinted Berlin, 1913), Tetens discussed the weaknesses of traditional metaphysics and proposed some remedies. He held that to reform metaphysics, the sources and development of metaphysical concepts must be investigated. The means of inquiry was "inner sense," or introspection. He tried to give purely psychological answers to psychophysiological problems on the one hand and to metaphysical problems on the other.

In this spirit, Tetens's major work, Philosophische Versuche über die menschliche Natur und ihre Entwicklung (Philosophical essays on human nature and Its development; 2 vols., Leipzig, 1777; reprinted Berlin, 1913), was an extended inquiry into the origin and structure of knowledge. He distinguished three faculties of the human mind: understanding, will, and feeling of pleasures and pains. He stressed the independence of the third faculty from the first two. The three may be reducible to one, but if so, according to Tetens, we cannot know it.

The mind is essentially active. Even sensation implies a reaction of the subject to the thing sensed. There are three fundamental activities of representation: perception, reflection (or abstraction from perceptions), and fiction (or the construction of new ideas out of perceived and abstracted representations).

Relations are established among perceived things by means of "primary original notions of relationships," or "forms"; one such form is causal connection. The three activities of representation together with the forms bring about the "concept of an object." Tetens proposed a rule for deciding whether something exists subjectively or objectivelywe attribute a sensation to a thing if the sensation is contained as a part in the entire sensation of the thing.

Tetens distinguished rational knowledge from sensible knowledge by its being general and necessary. Metaphysical first principles are undeniable because they are rooted in the essence of the ego. They are like natural laws to which the intellect is subjected. The intellector common senseand reason are governed by different kinds of laws, and the confusion between the two kinds of laws brings them into conflict.

Tetens discussed with great insight many other extremely complicated problems in metaphysics, ethics, the philosophy of education, and the philosophy of language. His Philosophische Versuche exerted a tremendous influence on Kant while he was writing the Critique of Pure Reason, and the many similarities between their doctrines are evident. Tetens's doctrines may be compared to Kant's even in their speculative power and importance.

See also Bonnet, Charles; Crusius, Christian August; Empiricism; Hartley, David; Helvétius, Claude-Adrien; Hume, David; Kant, Immanuel; Lambert, Johann Heinrich; Leibniz, Gottfried Wilhelm; Locke, John; Sulzer, Johann Georg; Wolff, Christian.


Brenke, M. J. N. Tetens' Erkenntnistheorie vom Standpunkte des Kritizismus. Rostock: Boldt'sche Hofbuchdruckerei, 1901.

Fuchs, Arnold. J. N. Tetens' pädagogische Anschauungen. Langensalza, 1918.

Golembski, W. "Die deutsche Aufklärungsphilosophie als Quelle des Transzendentalismus, I, Die Ontologie des J. N. Tetens." Bulletin International de l'Academie Polonaise des Sciences et des Lettres (1934): 167173.

Kuehn, Manfred. "Hume and Tetens." Hume Studies 15(2)(1989): 365375.

Lorsch, J. Die Lehre vom Gefühl bei Tetens. Giessen, 1906.

Schinz, M. Die Moralphilosophie von Tetens. Leipzig, 1906.

Seidel, Arthur. Tetens Einfluss auf die kritische Philosophie Kants. Leipzig, 1932.

Sommer, R. Grundzüge einer Geschichte des deutschen Psychologie und Aesthetik von WolffBaumgarten bis KantSchiller, 260302. Würzburg, 1892.

Störring, G. Die Erkenntnistheorie von Tetens. Leipzig, 1901.

Uebele, W. "Herder und Tetens." Archiv für Geschichte der Philosophie 18 (1905): 216249.

Uebele, W. J. N. Tetens nach seiner Gesamtentwicklung betrachtet mit besonderer Berücksichtigung des Verhältnisses zu Kant. Berlin: Reuther and Reichard, 1911.

Giorgio Tonelli (1967)

Bibliography updated by Tamra Frei (2005)