Johann Nicolaus Tetens was born in Tetenbüll, Schleswig, in 1738; he studied first in Rostock in 1755–1756 and then in Copenhagen after 1757, receiving his master's degree (Magister) in physics in Rostock in 1759. In 1760 he moved to the newly formed Academy in Bützow, where he became professor of physics and philosophy in 1763. He accepted an ordinary professorship of philosophy and mathematics at the University of Kiel in 1776 and was elected to the Royal Danish Scientific Society in 1787. Far from being an academic who would pursue only scholarly ends, Tetens was also interested in a variety of practical endeavors, from the administration of insurance plans to the functioning of dikes. From 1789 until his death in 1807, Tetens was a high-level financial administrator for several private and government institutions in Copenhagen.

Tetens published on a wide range of topics throughout his career in German, Danish, and Latin: in natural philosophy (on vis viva, the force of cohesion, friction, the effects of climate, the curative powers of magnets, and magnetic metal in Mecklenburg), mathematics (on the functions of curves, the principle of least difference, the formulae of polynomials, and the properties of the number nine), economics (on the national debt of England, the calculation of pensions, and Danish monetary policy), philosophical theology (on proofs of God's existence and the reality of our concept of God), and miscellaneous philosophical topics (on the differences between human beings, the rank ordering of the sciences, the various uses of human knowledge, the principles and uses of etymology, and the history of tolerance).