... where he commented on the Dialectic of Peter Ramus, as well as writing on logic and composing poetry.

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.

... 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.

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].

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 ...

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'.

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.

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.

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.

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.

... 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.

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.

... 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 ...

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.