The most important Serbian philosopher and famous scientist B. Petronijević was born 1875 in the Sovljak village near Ub in the impoverish, traditionally cleric family. Primary and secondary education he finished in Sovljak, Valjevo and Belgrade under harsh financial conditions. In the school he excelled with this knowledge. He was especially interested in philosophy, mathematics and physics. He started medical studies in Vienna but after the third semester he proceeded to the Faculty of Philosophy in Leipzig. He graduated there in 1897 yet in 1898 he defended his Doctorate in philosophy, physics and botany.
In Belgrade on the Department of philosophy he was from 1898 to 1927 in all professors levels on the University. During the First World War he lived and worked in London and Paris. From 1920 he was a member of the Serbian Royal Academy. He was precociously retired in 1927. Until the end of his life he was very active in philosophy and science in spite of large financial and other troubles. He deceased in Belgrade on 4th of March 1954.
Petronijević was completely devoted to philosophy and science. He spent his life in intensive work never accepting any social duties. In essence he was synthetic-deductive philosopher who divides the system of knowledge into three spheres: metaphysical, intermediary and empirical. He considered himself for born metaphysician" and devoted all his efforts into building of the original system of the spiritualisticobjective idealism. In that metaphysical system he introduced the theory of cognition and philosophy of nature. His starting stance mono-pluralism he connected with the originalempiric-rationalistic theory of cognition, with his own discrete geometry and philosophy of developing nature. He was strict finitst in everything. As synthetic philosopher and dialectician Petronijević tried to merge primary philosophic doctrines: in gnoseology, empirism and rationalism; in metaphysics, mo-nadology and substantialism; in ontology and methodology, dialectics and metaphysics (in Hegel's sense); science and religion, science and speculation and others. His main philosophic workPrinciples of metaphysics (I and II) was left undone.
As a philosopher and scientist, according to his own opinion, he published 53 original principles, discoveries and innovations. He considered that the highest level in science he reached in mathematics, especially with his original discrete and finite geometry. Time and space are real forms of the being and the space itself is simultaneous coexistence of real pointsand the fragments of the being in the time. That geometry mathematicians today consider as unusual, abstruse and not strictly mathematically founded. However, it is aloowed that it was not still adequately studied and it is possible that in its deepest essenceit has certain philosophicalfoundation and truthfulness. This mathematical quintessence is still not clear to anyone but it has to be discovered and further developed through strict matematization of Petronijević 's ideas. -He worked on other mathematical problems but was less original. For mathematician he demonstrated surprising wideness of knowledge and capability in that science.
In natural sciences Petronijević published many texts in palaeontology, biology, comparative anatomy, physics, chemistry, astronomy and the history of those sciences. His most significant results he achieved in the research of fossil birds. He discovered a number of details in the Archae-opteryx skeleton on which basis he separated the Berlin eyample into the new genus Archaeornis. From that fact he made important speculative conclusions about the origin, development, taxonomy and characteristics of the early birds. -After the extensive examination of five newly discovered early bird specimens all of his interpretations were abandoned. Only his real discoveries of the Archaeopteryx skeleton parts remained.
These parts were located with the aid of his original method of channelled dep preparation from the depth of the stone plate. The important place in the science remained for his other papers on fossil vertebrates. Specially fascinating and important are Petronijević 's contributions to the philosophy of natural sciences. Among them there are the explanation of the Dollo's law of irreversible evolution, the introduction of his own law of non-correlative evolution and detailed explanation of various segments of universal evolution.
With his whole philosophical, philosophically-scientific and scientific activity Petronijević, in the line of earlier empiric and critical metaphisicists (Lotze, Herbart, Hartmann, Volkelt), he directly significantly contributed and made possible formation of modern sphere of cognition which is today known as methascience.
By the power of his analytical and synthetic opinions, by their width and depth, than by the creativity of his intuition and especially by the consequentiality and originality of conceptions, Petronijević achieved the peak of metaphysical thought in our country. Those same qualities enabled significant achievements in science and philosophy of science to him. Because of that Petronijević relished considerable credit in Europe and the whole world, which is still the honour of Serbian science and philosophy.
Authors: Grubić, Aleksandar; Prvanović, Mileva; Stojković, Andrija