Nicolaus Steno (Niels Stensen, 1638-86) is considered to be the founder of geology as a discipline of modern science, and is also considered to be founder of scientific conceptions of the human glands, muscles, heart and brain. With respect to his anatomical results the judgment of posterity has always considered Steno to be one of the founders of modern anatomy, whereas Steno's paternity to the methods known to day of all students of geology was almost forgotten during the 130 yr from 1700 to 1830. Besides geology and anatomy there are still important sides of Steno's scientific contributions to be rediscovered. Steno's general philosophy of science is one of the clearest formulated philosophies of modern science as it appeared during the 17th Century. It includes • separation of scientific methods from religious arguments, • a principle of how to seek "demonstrative certainty" by demanding considerations from both reductionist and holist perspectives, • a series of purely structural (semiotic) principles developing a stringent basis for the pragmatic, historic (diachronous) sciences as opposed to the categorical, timeless (achronous) sciences, • "Steno's ladder of knowledge" by which he formulated the leading principle of modern science i.e., how true knowledge about deeper, hidden causes ("what we are ignorant about") can be approached by combining analogue experiences with logic reasoning. However, Steno's ideas and influence on the general principles of modern science are still quite unknown outside Scandinavia, Italy, France and Germany. This unfortunate situation may be explained with the fact that most of his philosophical statements have not been translated to English until recent decades. Several Latin philologists state that Steno's Latin language is of great beauty and poetic value, and that translations to other languages cannot give justice to Steno's texts. Thus, translations may have seemed too difficult. Steno's ideas on the philosophy of science appear in both his many anatomical and in his fewer geological papers, all of which with one exception (in French) were written in Latin. A concentration of his philosophy of science was given by himself in his last scientific lecture "Prooemium" (1673), which was not translated from Latin to English before 1994. Therefore, after the decline of Latin as a scientific language Steno's philosophy of science and ideas on scientific reasoning remained quite unknown, although his ideas should be considered extremely modern and path finding for the scientific revolution of the bio- and geo-sciences. Moreover, Steno's philosophy of science is comparable to Immanuel Kant's 80 yr younger theory on perception, Charles S. Peirce's 230 yr younger theory on abduction, and-especially-Karl R. Popper's 300 yr younger theory on scientific discovery by conjecture and refutation. The general outset of Steno's philosophy of science constitutes an important step from the Medieval's and the Renaissance's way of thinking into the 17th Century's appearance of modern sciences and the 18th Century's Enlightenment. The 18th Century's as well as present day's dichotomy of science into the traditional creationistic and the new historical interpretations to some extent can be traced back to Steno and his methods.