In this article, three concepts that constitute the pillars of sciences, namely the subject, principle and problem, will be examined relying on Avicenna’s (d. 428/1037) book of Burhān. These three concepts, which generally determine the scope of scientific research and the principles on which it should be based, were introduced systematically for the first time by Aristotle (d. 322 BC) in the history of thought. Through these concepts, philosophical sciences could be distinguished from one another and it became possible for each science to examine specific parts of existence. This distinction, which was also adopted by the scholars of Islamic thought, has presented such an integrity that neither philosophical disciplines nor religious sciences could remain indifferent. As a matter of fact, especially in the later period of theologicians, the information was considered as science only if it was based on these three concepts. Therefore, it can be asserted that these three concepts were considered as the measure of scientific activity, first by peripatetic philosophy and later by other disciplines.