This paper investigates the epistemological role of miracle (muʿjiza) and infallibility (ʿisma) in grounding the authority of prophetic testimony in the thought of Khwāja Naṣīr al-Dīn al-Ṭūsī. In the contemporary world—dominated by scientific rationality, empirical verification, repeatability, and falsifiability—religious beliefs face serious epistemic challenges. Unlike scientific knowledge, which relies on repeatable experiments and observable data, religious belief is often based on historical testimony and claims about the unseen. This raises a central question: how can one rationally trust the testimony of a prophet who claims access to a transcendent and unobservable realm?
Ṭūsī emerges as one of the most significant thinkers who constructed a systematic, rational framework for grounding trust in prophetic testimony. Drawing on Avicennian philosophy and Imāmī kalām, he proposes a three-stage model: (1) establishing rationally the existence of God, the possibility of revelation, and the necessity of prophecy; (2) confirming a particular prophetic claim through miracle, understood as divine authentication; and (3) grounding the continuing epistemic authority of the prophet’s statements in infallibility. This triadic model demonstrates that for Ṭūsī, belief in prophecy is neither blind imitation nor skepticism, but a rationally justified stance.
To contextualize Ṭūsī’s approach, the paper first discusses the epistemology of testimony. Testimony accounts for a substantial portion of human knowledge—covering historical, scientific, and everyday facts alike. Two dominant approaches structure the field: reductionism and anti-reductionism. Reductionists maintain that testimony is justified only when supported by independent evidence, while anti-reductionists argue that testimony is a basic source of knowledge, justified by default unless there is positive reason for doubt. In religious contexts, testimony becomes even more complex due to supernatural content, claims to infallibility, and the moral and existential implications of accepting or rejecting prophetic authority.
Ṭūsī’s epistemology of prophecy responds to these challenges in a structured manner. First, he argues that human beings need social life, which requires law, and only a divinely commissioned lawgiver can provide complete and flawless legislation. Moreover, human intellect alone is insufficient for grasping all truths—especially the details of divine commands and the nature of the afterlife—thus necessitating divine guidance. These arguments establish prophecy as rationally necessary, even before addressing any specific prophetic claimant.
In the second stage, Ṭūsī defines miracle as a supernatural act accompanied by public challenge (taḥaddī), which is beyond human capacity, inimitable, and occurring exactly as claimed by the prophet. These conditions transform a miraculous event into an epistemic sign. From an epistemological perspective, the miracle functions as external divine certification of the prophet’s truthfulness. Ṭūsī argues that it would be irrational for God to grant the power to perform a true miracle to a liar; thus, the miracle establishes the sincerity and veracity of the claimant. Once a miracle meeting the required conditions is verified, it becomes a sufficient argument for the truth of the prophetic claim.
The third stage focuses on infallibility. Ṭūsī defines infallibility as a divine grace that removes the motivation for sin or error while preserving human freedom. Infallibility guarantees that the prophet will not err in receiving, preserving, or conveying revelation. From the standpoint of contemporary epistemology, infallibility can be interpreted as maximal epistemic reliability. In reliabilist terms, the prophet’s cognitive processes consistently generate true beliefs; in virtue epistemology, the prophet exemplifies perfect epistemic virtue, thus possessing supreme epistemic authority. This means that once prophecy and infallibility are established, one is epistemically justified in accepting the prophet’s testimony without needing to examine each claim independently.
The article also addresses modern challenges such as religious diversity and Hume’s alleged circularity between miracle reports and prophetic testimony. Drawing on externalist epistemology, the paper argues that the mere existence of competing religious claims does not undermine the justification of a believer’s testimony-based beliefs. What matters is the reliability of the belief-forming process, not universal consensus. Regarding Hume’s charge of circularity, the paper explains that many miracles are reported by multiple independent witnesses, that Hume’s own argument relies on testimony to establish a “uniform experience,” and that in Ṭūsī’s framework, miracles operate alongside other rational premises rather than in isolation.
In conclusion, the study demonstrates that Ṭūsī provides a sophisticated and rational model for justifying prophetic testimony. By combining external divine verification (miracle) with internal epistemic security (infallibility), Ṭūsī constructs a framework that bridges classical Islamic theology and contemporary epistemology of testimony. His model offers valuable insights for current debates on religious epistemology, testimonial justification, and the rationality of faith.