Mulla Sadra Shirazi (1571-1636) explains the process of knowledge in three different phases. Prior to this, he introduces the differences between the presential knowledge (al-?ilm al-huzuri) and acquired knowledge (al-?ilm al-husuli). The founder of the Islamic Transcendent Philosophy states that the first form of knowledge is direct, because no terms appear in it, whereas the second is realized by means of concepts. For this reason, epistemic error is not possible in the presential knowledge, because the subject of the knowledge is present in the knower. After this introduction, Mulla Sadra explains the process of certain knowledge. He claims that in the first phase man learns of his existence in a present and immediate way. In the second phase - which is also within the scope of the knowledge by presence - man considers the relationship between his existence and some aspects of his existence, and thus immediately draws conclusions and generalizes certain principles such as causality (al-?ilija) and causal relatedness (as-sinhija). Finally, in the third phase, he explains various divisions of acquired knowledge.