Joachim Jungius was given the name Joachim Junge (or Jung) when he was born; Jungius is the Latin version of Junge which he used in all his publications. His father, Nicolaus Junge, was a teacher at the Gymnasium St Katharinen in Lübeck and his mother was Brigitte Holdmann, the daughter of Joachim Holdmann who was a minister in the Lutheran Cathedral in Lübeck. However, Nicolaus Junge was murdered when Joachim was only two years old and, in 1589, Brigitte married Martin Nordmann who was a teacher at the Gymnasium St Katharinen in Lübeck. Joachim was brought up by his mother and step-father. He attended the Gymnasium St Katharinen in Lübeck until 1605 :-
... where he commented on the Dialectic of Peter Ramus, as well as writing on logic and composing poetry.
In May 1606 he entered the University of Rostock, rather later than one might expect due to his delicate physique, where he studied metaphysics. Hans Kangro writes :-
At Rostock Jungius studied with Johann Sleker, from whom he learned metaphysics in the tradition of Francisco Suarez and his school. In general, however, he preferred to concentrate on mathematics and logic.
On leaving Rostock, Jungius matriculated at the University of Giessen in May 1608 and he was awarded an M.A. on 22 December 1608. In 1609 he was appointed as a professor of mathematics at Giessen and there he taught pure mathematics, the physical applications of mathematics to optics, harmonics, astronomy and geography, and the mechanical applications to the theory of refraction, hydrostatics and architecture. In his inaugural lecture, delivered on taking up his appointment at Giessen, he spoke of his belief that mathematics was the basis for all scientific subjects and, as such, was of vital importance in teaching. He studied the new ideas in algebra which had been introduced a few years earlier by François Viète in his In artem analyticam isagoge. In 1612, along with his Gissen colleague Christoph Helvig, Jungius went to Frankfurt for the coronation of Matthias, King of Hungary and King of Bohemia, as the Holy Roman Emperor. While on this journey he observed sunspots; at the time Galileo (March 1612), David Fabricius and his son Johannes (1611), and Christoph Scheiner (January 1612) were all claiming priority in their discovery. (In fact unknown to all of them Thomas Harriot has priority, beginning to record sunspot observations on 8 December 1610.)
It was while on this visit to Frankfurt that Jungius met with the educational reformer Wolfgang Ratke who had developed his own system of education. Jungius was very interested in Ratke's ideas and together they discussed starting schools in Augsburg and Erfurt which would teach according to Ratke's system. In 1614 Jungius resigned his position at Giessen with the idea that he would devote himself to educational reform, but he soon decided that he wanted to increase his knowledge of medicine. He enrolled at the University of Rostock to study medicine in August 1616. After some time studying there, he went to Padua to continued medical education:-
... he must have found the atmosphere of Padua congenial, because of the school's emphasis on a research-oriented natural philosophy, medical training, and mathematics.
He received a medical degree from the University of Padua on 1 January 1619. Thereafter Jungius practiced medicine at Lübeck from 1619 to 1623, he held the chair of mathematics at the University of Rostock from 1624 to 1625, practiced medicine at Brunswick and Wolfenbüttel in 1625 and then from 1626 to 1628 he again held the chair of mathematics at the University of Rostock. For one year in 1625 he held the chair of medicine at the University of Helmstedt in addition to practicing medicine. When giving his inaugural address on taking up the chair at Rostock, Jungius gave a similar address to the one he had given at Giessen, stressing his belief that mathematics was the basis for all scientific subjects. These years from 1619 to 1629 were ones during which he was at the height of his powers, able to use knowledge and skills in many different areas across a whole spectrum of scientific activities. Also during this period he married Catharina Havemann, the daughter of Brauers Valentin Havemann from Rostock, on 10 February 1624. Perhaps the mathematical work which occupied him most over these years was his work reconstructing Apollonius's Plane Loci which, although lost had been described by Pappus of Alexandria in Book VII of his Collection. Jan Hogendijk explains :-
Jungius worked on [a reconstruction of Apollonius's Plane Loci] from 1622 to 1629, and the work was completed by his pupil Weland in the period between 1638 and his death in 1641. Around 1670 the re-construction was annotated by Johannes Muller, who evidently planned to prepare the work for the press. However, the work remained in manuscript until [it was published in 1988].
The reason that Jungius stopped working on the reconstruction in 1629 was that in that year he moved to Hamburg where he became professor of natural science at the Akademisches Gymnasium. Administrative duties prevented him from completing the reconstruction of Plane Loci. He became Rector of the Gymnasium and also of the Johanneum, a Latin school which shared the same premises as the Akademisches Gymnasium. On 19 March 1629 he gave his inaugural oration, similar to the one he had given in Giessen and Rostock, on the use of mathematics in studying liberal arts. Many professors begin their careers teaching in secondary schools, but few make the move which Jungius did and leave university education to teach in schools. It was a move made because of his desire to improve school education and he took charge of the Akademisches Gymnasium and the Johanneum, about fifteen years after it was founded, at a time when it was in difficulties. Under Jungius's leadership the school prospered and many pupils outwith Hamburg or the surrounding area, moved there to benefit from the education. However, he faced difficulties during the 1630s :-
His wife, Catharina ... died on 16 June 1638. During the 1630's, too, he became subject to the envy of his colleagues and even to attacks by the clergy, despite his devout Protestantism. He was thereafter reluctant to publish his writings and left some 75,000 pages in manuscript at the time of his death, of which two-thirds were destroyed in a fire in 1691 ...
While at the Academic Gymnasium in Hamburg, where he taught until 1640, Jungius delivered "physics" lectures which were published by Christopher Meinel in the 1980s. Owen Hannaway writes :-
Copies of the course have survived in a number of manuscript recensions, some revised by Jungius himself. ... In spite of the title [physics], these are not concerned with the subject matter of Aristotle's 'Physics', nor with the new mathematised physics. Instead they concern substantial change as defined in Aristotle's 'De generatione et corruptione' and Book IV of the 'Meteorologica'.
Walter Pagel writes in  about the wide-ranging contributions which Jungius did publish:-
Jungius was primarily an explorer of nature, interested in the composition of matter, the reaction of bodies with each other and the techniques which would best allow insight into their working. It was notably in the fields of botany and chemistry that he found the empirical directives and morals for his epistemology. It was thus that his 'Logica Hamburgensis' became something profoundly different from the usual textbooks of syllogisms on Peripatetic lines.
The Logica Hamburgensis (1638) of Jungius, composed for the use of pupils at the Akademisches Gymnasium, presented late medieval theories and techniques of logic. In it he discussed valid oblique cases of arguments that do not fit into simpler forms of inference. For example:
The square of an even number is even; 6 is even; therefore, the square of 6 is even.
The oblique case of an even number had to be put into the subject position so that standard arguments could be used. Aristotle had also dealt with this type of logical argument.
Howard Bernstein gives the following overview of Jungius's contributions :-
Joachim Jungius was a German polymath somewhat in the Leibnizian tradition of encyclopaedic range as well as originality in several domains of knowledge, including logic, mathematics, and natural philosophy. While Leibniz administered a princely library, Jungius assembled an extensive private book and manuscript collection over a long and intellectually ecumenical career. ... At different times in his career, Jungius's scholarly "centre of gravity" ... shifted: from his early training in the late scholasticism of Francisco Suarez and his like, to astronomy, logic and mathematics, educational reform, medicine, and chemical philosophy (in his case corpuscularism), to an ambitious program to organise, systematise, and taxonomise - as well as further to contribute to (based on a mathematical paradigm) - the sum total of human knowledge.
In mathematics Jungius proved that the catenary is not a parabola (Galileo assumed it was). He was one of the first to use exponents to represent powers and he used mathematics as a model for the natural sciences. As well as mathematics, Jungius was interested in natural science. Audrey Davis in  (reviewing Kango's book ) writes:-
Kangro's most fortunate discovery, in his own estimation, was a fragment that reflects Jungius's fundamental ideas on logic applied to science. [It is] entitled the "Protonoeticae philosophiae sciagraphia" .... From it we learn that Jungius was confident of predicting and explaining natural phenomena by adopting the natural laws that he distinguished. He differentiated three grades of knowledge: Empiricus, Epistemonicus, and Heureticus. Empiricus remained verifiable through experience, Epistemonicus is grounded in principles and rules - as are the axioms of Euclid's geometry - and Heureticus reveals new methods for the solution of problems previously insoluble. These three methods replaced the prevalent ancient form of logic based on the syllogism. In brief, Jungius transformed the relevant parts of the Peripatetic notion of physics into what was to become physical chemistry by the analysis of unique experiences and experiments and the mathematical method of synthesis.
In particular, Jungius is known for his atomic theories. Christoph Meinel  writes about Jungius's scientific approach:-
The closest amalgamation of the concepts of atom, element, and pure substance that can be found before the nineteenth century, however, was reached by Joachim Jungius in 1632. Here the gap between perceivable and experimentally accessible qualities of macroscopic bodies and those of the ultimate constituents of matter had almost disappeared. ... In [Jungius's] opinion a distinct science of nature required above all a finite number of principles, just as Euclidean geometry relies upon a small number of basic entities such as the point, the line, and the angle. Jungius's attempt to rebuild the system of physical knowledge belongs to the widespread quest for making both philosophy and natural science as axiomatically structured as geometry. In contrast to most of his contemporaries, Jungius insisted that only the evidence of sensuous experience and an inductive methodology would lead to the identification of these ultimate units of reality. ... Jungius used the magnifying glass to study textile fabric and apparently homogeneous substances such as polished surfaces. He observed that they were in fact always heterogeneous if viewed through a microscope (anchiscopium). In 1633, commenting on Sennert's 'Epitome scientiae naturalis' of 1618, in which Sennert had shown that arguments from geometry about divisibility and continuity must not be applied to the physical sciences, Jungius remarked that until then no physical body had ever been proved to be entirely homogeneous. For no surface could be so smooth that one could not think of a more powerful microscope that would reveal its true discontinuity. Consequently, Jungius categorically stated that continuity was foreign to the realm of sensuous experience. On the other hand he had to admit that if there were no truly continuous parts in the end, infinite progression and divisibility would result. This was the vicious circle of every observational approach to the atoms.
This approach led Jungius to a concept of an element :-
... he comes to list a number of substances (silver, gold, mercury, sulphur, salt and some others) the particles of which he thought to be not subject to further diacrisis, e.g. through acid or preferably fire. They are - so he believed - really homogeneous and therefore true elements.
He was led to make important chemical discoveries as Robert Multhauf describes in :-
In 1642 the little remembered German chemist, Joachim Jungius, published a criticism of contemporary mineral chemistry which represents a step in the development of the chemical theory comparable to that of Agricola with respect to the physical theory. Jungius begins with a common criticism of the chemical system, the impossibility of obtaining from metals any alleged elementary salt. But he goes on to suggest that blue vitriol (copper sulphate) is a combination of copper with "spirit of sulphur," and that the proximity of the more imperfect metal, iron, presents the spirit of sulphur with a combination for which it has a greater sympathy. Hence it releases the copper. A similar replacement occurs when copper itself is introduced into a solution of silver in aqua fortis. Thus the fact that metals can exist in the form of salts and liquids does not, according to Jungius, prove that salts and liquids exist as ingredients of metals.
Finally let us quote the opinion of one of Jungius's contemporaries. John Pell wrote :-
... there are few men that have not some idol, some man or woman whom they esteem, and admire, above the rest of mankind and Jungius is mine. ... I profess to expect more solidity in Jungius's writings than in any other man living ...
Gottfried Wilhelm Leibniz, who was only eleven years old when Jungius died, wrote:-
While Jungius of Lübeck is a man little known even in Germany itself, he was clearly of such judiciousness and such capacity of mind that I know of no other mortal, including even Descartes himself, from whom we could better have expected a great restoration of the sciences, had Jungius been either known or assisted.
Article by: J J O'Connor and E F Robertson