The Ontological and Epistemological Position of Priori in Explanation of Substance in Aristotelian Sense

Philosophical movements after renaissance specifically during eighteenth century have been commenced by Kant and continued by his impact. Then Aristotle’s philosophy has been forgotten for being non- critical and dogmatic. In fact, it is claimed that his philosophy elucidates the episteme by deriving the intelligible or quiddity from the objects. This philosophy does not need to have a research on the conditions of priori to the experience. It does not research, therefore, on the authenticity of knowledge and awareness through validity of such conditions. The present article illuminates that the Aristotle’s metaphysics is not based on the deriving quiddity from the external world, but it researches on the conditions prior to the experience by a specific method. For the conditions and principles which have been discussed in the metaphysics, are the principles of being qua being which precede the experiment. These principles and elements are hidden in the definition of quiddity. Since the whatness is combined of the form and matter, these principles denote to the world concrete elements and then insist on the experimental values. The substance, in this perspective, is explained as a priori ontology on which the epistemology is based.