Al-Ghazali’s most famous victory was also the source of the deepest objections to his legacy. The first and most enduring criticism is that by weakening necessary causation he imperiled the explanatory ambition of philosophy and science alike. If fire does not burn by nature, then what exactly is gained by distinguishing causes from mere occasions? The world may remain orderly, but its order risks becoming inscrutable habit rather than intelligible structure. That was not a merely abstract worry. In the history of Islamic intellectual life, this issue mattered wherever scholars, jurists, physicians, and astronomers depended on the regularity of nature to make arguments, interpret signs, or preserve method. A world of repeated divine custom could still be navigated, but it could also become harder to explain with confidence, harder to systematize, and harder to defend against rivals who claimed more rigorous demonstrations.
This objection was sharpened by Ibn Rushd, known in Latin as Averroes, in Tahafut al-Tahafut, the Incoherence of the Incoherence. He argued that al-Ghazali had failed to distinguish what is merely customary from what is demonstrable by rigorous inquiry. On the standard reading of Averroes, the problem was not only metaphysical but epistemic: if one can dismiss necessary causal connections too easily, then one opens the door to arbitrary intervention and undermines the confidence required for natural knowledge. The stakes were high because the issue was not a minor technicality. The question of causation sat at the center of how learned readers defended the reliability of observation, the authority of demonstration, and the possibility of a disciplined philosophy that could speak about the world without collapsing into uncertainty. When Averroes answered al-Ghazali, he was not simply defending Aristotle for its own sake; he was defending the conditions under which inquiry remains inquiry at all.
A second criticism came from within theology. Some Ash'arite and later Sunni readers admired his piety but worried about the force of his skeptical passages. If the senses and the intellect are both vulnerable, then by what right does revelation claim authority for the ordinary believer? Al-Ghazali’s answer is that revelation is authenticated through a broader economy of guidance, but critics could still ask whether the skeptic’s ladder has been kicked away too quickly. The tension is acute: the very method that humbles reason must stop short of dissolving the grounds on which religious teaching stands. Here the problem is not merely theoretical. If the ordinary believer cannot trust the senses, and cannot trust unaided reasoning, then every stage between daily life and religious certainty becomes exposed. The whole architecture of instruction, from elementary learning to the madrasah curriculum, depends on keeping that anxiety within bounds. Al-Ghazali knew this, and his critics knew it too.
There is also a philosophical worry about the relationship between doubt and certainty in his autobiographical narrative. Did he really pass through a radical skeptical abyss, or is the account stylized for apologetic purposes? Scholars disagree about how literally to read the crisis described in al-Munqidh min al-Dalal (Deliverance from Error). Even if we bracket biography, the narrative functions as a philosophical drama: doubt strips away intellectual vanity, but one may wonder whether the desired outcome was already built into the story. That question matters because the text is not merely private confession; it is a public document of intellectual conversion, a testimony about how a thinker moved from confidence to crisis and from crisis to certainty. If the account is dramatized, then the drama itself becomes part of the argument. If it is literal, then it is one of the most consequential moments in medieval intellectual autobiography. Either way, the stakes are transparent: the story legitimizes a method of purification through doubt, but it also risks being read as a carefully arranged pathway to a conclusion already chosen.
A third objection concerns the treatment of philosophy itself. Al-Ghazali is often praised for knowing the philosophers so well, yet his selective condemnation in Tahafut al-Falasifa can look asymmetric. He targets specific doctrines—eternity of the world, divine knowledge of particulars, bodily resurrection, and causation—but leaves enough of the philosophical edifice intact to make one ask why the enterprise should be condemned under a single name. This was a polemical choice with real force, but it also invited later readers to accuse him of overstating the threat. The argument had a sharp edge because it was aimed at a recognizable intellectual class, the falasifa, whose prestige rested on inherited demonstration and systematic scope. By singling out these doctrines, al-Ghazali did not merely critique isolated claims; he identified points at which, in his view, philosophy crossed the line from disciplined reasoning into doctrinal overreach. Yet that very precision allowed opponents to say that he had attacked a school by choosing its most vulnerable propositions, rather than by meeting it on its strongest ground.
A concrete example helps. The doctrine that God knows particulars seems to al-Ghazali indispensable for providence, prayer, and judgment. But the philosophical account he rejects was not simply casual negligence; it aimed to protect divine immutability and intelligibility. Thus each side accuses the other of sacrificing an attribute of God: one side says philosophy empties providence, the other says theology anthropomorphizes the divine. The argument is not between thought and piety, but between two demanding visions of transcendence. That is why the controversy endured. The issue was not whether God exists, but how divine knowledge can be described without diminishing divine perfection. In that dispute, every formulation carried risk. To insist too strongly on particulars seemed to make God look changeable; to refuse particulars seemed to make divine care abstract and remote.
A fourth tension appears in his relation to Sufism. The inward path promises certainty through purification, but it also raises the specter of subjectivity. How does one distinguish genuine unveiling from self-deception? Al-Ghazali answers with discipline, law, and the authority of tradition, yet the problem never disappears entirely. The very intimacy of spiritual knowledge makes it vulnerable to abuse by pretenders, and he knew this well. His own life had taught him that charlatanry flourishes wherever inner experience is prized. This is one reason his writings repeatedly insist that spiritual knowledge cannot simply float free of ethical and legal formation. The path is inward, but it is not ungoverned. That insistence gives his mysticism structure, but it also reveals the pressure under which it operates: the more one values inner certainty, the more one must police claims to have attained it.
There is even a political tension. His critique of the philosophers helped secure a Sunni theological culture in which metaphysics was more carefully policed, but it also contributed to later narratives that blamed him for the supposed decline of philosophy in the Islamic world. That story is too simple and too often repeated, yet it reflects a real fear: when one disciplines reason too successfully, one may discourage the very speculative energy that produces intellectual growth. The issue was never merely scholarly. In a broader institutional world of teaching, patronage, and reputational struggle, the balance between orthodoxy and inquiry mattered for what could be taught, which books could be trusted, and what kinds of intellectual ambition could survive.
And yet the objections do not simply refute him. They reveal the cost of his achievement. He wanted a knowledge that was both humble and sure, both inward and public, both critical and obedient. That is an unstable balance. If one presses too far toward skepticism, revelation loses its footing; if one presses too far toward certainty, the heart becomes complacent. Al-Ghazali stands at the point where these pressures meet, and his thought can be read as an attempt to survive them without surrendering either truth or devotion.
The fire of criticism, then, does not leave only ashes. It clarifies what his project demanded from its followers: not a passive assent, but a willingness to let reason be judged by a higher standard while still preserving its dignity. The question that remains is whether later thinkers could inherit that difficult balance, or whether they would turn him into something simpler than he was.