There were three different ways in which scholars in the latter half of the 16th and in the 17th century approached the study of nature: the traditional approach of scholastic Aristotelianism, the mathematical-mechanical approach represented mainly by Descartes, and the “chemical” approach based on Paracelsus’ philosophy of nature. Comenius in his works about nature adopted the Paracelsian approach. The science of nature was of great importance to Comenius, because the knowledge of nature underlay his theory of the knowledge of general forms of the world, ideas and their relationships, whereby the natural philosophy acquired a universal position in his pansophy. Besides minor works of a textbook character which are preserved in the so-called Leningrad Manuscript, natural philosophy is dealt with in his work Physicae synopsis, in some parts of his Janua linguarum and in the fourth and fifth grades of his Pansofia. The fourth grade gives the picture of nature itself, as in appears to man, the fifth grade explains how man, by using and imitating nature, transforms the world and creates new forms. Thus the fourth grade deals with what we would now call theoretical natural science, and the fifth grade with applied natural science. In the description of nature Comenius proceeds from a mosaic viewpoint, his standpoint is the organic conception of the world and he develops its picture from the fundamental principles right up to man, so that besides mathematics, mechanics and chemistry we also find here astronomy, meteorology, mineralogy, botany, zoology and anthropology (in the sense current in those times, of course). In the fifth grade, which shows great gaps and in the second part is rather confused, we learn about Comenius’ views on applied natural sciences, which he classifies in such a way as to make them correspond to the theoretical sciences in the fourth grade and describes how man uses individual objects of nature for his benefit. Thus we learn about pyrotechnics (the use of fire), uranotechnics (use derived from the knowledge of celestial phenomena), aerotechnics (the^use of the air), hydrotechnics (the use of water) etc. Botany and zoology have their coun terparts in phytotechnics and zootechnics, anthropology in macrobiotics, hygiene and medicine as regards the physical aspect, and in pedagogy as regards the mental aspect. The remaining part of the fifth grade is rather incomplete and the subject- matter is given at random. Comenius’ work makes us see his real honest efforts to grasp the natural sciences and his great diligence which makes itself felt especially in the fact that before under taking this work he had studied practically all the older and contemporary sources dealing with individual fields of nature study. It is difficult to give a general judgment on his work. Some of his explanations are disconnected and the work as a whole, although he tried to include some of the then modern views in it, contains too many ideas which were out of date even in his times.