Mīrzā Mahdī is known for his anti-philosophical and anti-mystical approach towards Islamic scripture, namely the Qurʾān and Sunna. This is an account of his intellectual life which became the main impetus behind a scriptural school of thought which later rose to fame as Maktab-i Tafkīk (The School of Separation). The concept of separation rather resembles a claim to independence for kalām. Mīrzā, like some other Muslim scholars, strongly believed that Hellenistic philosophy and mysticism are commodities wrongly integrated into the Islamic texture, and with rather a sinister intention. The problem with these beliefs, at a deeper level, is an epistemological debate over the territory of intellect (al-ʿaql), or, in other words, over the right of interpretation of the Text. Mīrzā maintained that the conclusions of these two rivals are not only wrong, but also deceptive and misleading. He, intelligently and repetitively, wraps the two together and stigmatizes them by calling them human knowledge, putting them in sharp contrast with divine knowledge (al-ʿulūm al-ilāhī), which is, in his terminology, Islamic Scripture. He draws the battle lines on two levels: firstly, by showing self-contradiction within philosophy and mysticism, and, secondly, by exposing contradictions between their outcomes and the text. This argument, probably for many, echoes the well-worn debates between ashʿarīs and muʿtazilīs, or later in a more Shīʿī ambiance, between akhbārīs and uṣūlīs. It is true, however, that the conflict for Mīrzā is more considerable in terms of doctrine. This research tries to find the exact boundaries of intellect in Mīrzā Mahdī ’s thought by which he re-defines the functionality of it in two main realms: belief and jurisprudence. It would be much easier to understand him if he had simply rejected thinking, or augmentation had pushed him into the abyss of irrationalism, but the point is that Mīrzā Mahdī is a scriptural Shīʿī scholar who thinks and argues, and, at the same time, endeavours to highlight the borders between a revelatory method of thinking and the one used by philosophers, which he calls human method, and believes is made of their systematic mistakes. On the other hand, Mīrzā, with a prominent name in anti-mystical challenges, calls for an easy and amassable personal experience (wijdān) which imperceptibly draws him to the threshold of mysticism. He invites everyone to experience the text, and again, to avoid a mystical method of experiencing it. Having said this, the purpose of this thesis is to specify the exact definition of epistemological means and the functionality of them, in Mīrzā Mahdī ’s view, by examining his ideas in the two main realms of doctrine and jurisprudence. It will be seen that Mīrzā uses the same method in both fields; however, the way he approached and publicized them, and consequently, the way that his pupils delivered and promoted his ideas, are different. The heritage of Mīrzā Mahdī Iṣfahānī has always been subject to conflicting debates between his zealot advocates and his harsh opponents. In this research, hopefully one has the opportunity to read his intellectual life in a contextualized way. I have been in touch with the most prominent scholars of the School for more than twenty years and attended their classes. However, I have had this chance to try, myself, to critically examine his philosophies and present them to academia.