Did al-Ghazali lead to decline of science in Islam as Neil Tyson claims?

Question

The astrophysicist Neil deGrasse Tyson has said that during the Islamic Golden Age, especially in Baghdad, science and discovery flourished for a few centuries. Then an Islamic scholar named al-Ghazali became prominent, whose ideas took root. Among these was something along the lines that mathematics was, to use Tyson's words "the work of the devil".

I've listened to many of Tyson's talks, and he's mentioned this many times. Today I came across the Wikipedia article for al-Ghazali and thought I'd spend some time reading about him. He was a rather influential Islamic scholar in many ways, but specific to the claim that his philosophy led to the decline of science within the Islamic world, I only found the following:

His reforms are widely seen as having initiated the decline of scientific research in the Islamic world.[by whom?][citation needed] Against this view, Saliba (2007) has given a number of examples especially of astronomical research flourishing after the time of al-Ghazali
Wikipedia article

Here is a video of Tyson making this claim. Sorry about the disputatious annotations made by the poster, but this was the first result I got for "Tyson al-Ghazali".

Is there any evidence that al-Ghazali said something like manipulating numbers or math is the work of the devil, or maybe sinful, or immoral? And as corollary to that, did he damage the spirit of scientific inquiry in the Islamic world?

Here is a quote written from one of the versions, found in video link 2 below:

"And in that interpretation (al-Ghazali's) it included the perspective that the manipulation of numbers is the work of the Devil. This cuts the kneecaps out of any mathematical advances that would unfold."

Links to other occasions he's said this before, here are two:
video 1
video 2

Edit: OK, I'm pretty sure I know what happened. Steven Weinberg is a physics Nobel laureate and acquaintance of Neil Tyson. Steven Weinberg is critical of religion, and has written:

"Alas, Islam turned against science in the twelfth century. The most influential figure was the philosopher Abu Hamid al-Ghazali, who argued in The Incoherence of the Philosophers against the very idea of laws of nature, on the ground that any such laws would put God’s hands in chains. According to al-Ghazali, a piece of cotton placed in a flame does not darken and smoulder because of the heat, but because God wants it to darken and smoulder. After al-Ghazali, there was no more science worth mentioning in Islamic countries."

Here is a video of Weinberg explaining this, just before Neil deGrasse Tyson comes to the podium to do his talk. It's possible that Neil Tyson's explanation of al-Ghazali has come from what Weinberg has told him.

Answer 1

This is an old myth from the days of Orientalism. Unfortunately Wikipedia is often edited precisely by people who have simply seen popular accounts by people like Tyson (or Skeptoid podcast, or The New Atlantis) produced with no understanding of the history of science or human thought. The fact is that Ghazzālī nowhere professed that reason or knowledge is useless. On the contrary, he tried to construct a better model of human reason and natural knowledge than past philosophers, hence the title of his book The Incoherence of the Philosophers. The "philosophers" in the title are literally "lovers of knowledge" (φιλόσοφος) from the Platonic tradition; Ghazzālī is not criticizing knowledge itself. In the words of a historian of philosophy,

Ghazali makes it plain that his purpose is to refute the Islamic philosophers' metaphysical theories and not their natural science. [...] Indeed, the misguided zealot who attacks science in the mistaken belief that he is defending religion, inflicts damage, not on science, but on religion. He inflicts this damage, Ghazali argues, precisely because science is demonstrable and certain. If it does, in fact, contradict religion, then it is the latter that becomes suspect and not science.

Michael Marmura, "Ghazali and Demonstrative Science." Journal of the History of Philosophy, Volume 3, Number 2, October 1965, pp. 183-204

Or to quote Ghazzālī's own words,

The greatest thing in which the atheists rejoice is for the defender of religion to declare [that the results of an astronomical observation] are contrary to religion. Thus, the [atheists'] path for refuting religion becomes easy if the likes [of such an argument] are rendered a condition [for its truth].

Quoted in Basit Bilal Koshul, "Ghazzālī, Ibn Rushd and Islam's Sojourn into Modernity: A Comparative Analysis" Islamic Studies Vol. 43, No. 2 (Summer 2004), pp. 207-225

Ghazzālī lived from 1058 to 1111 AD. His critique of religionists' blind devotion to Aristotelian metaphysics would emerge in France over a century later (the famous Condemnations of 1210 and 1277). A history of science writer and evangelical Christian, Richard P. Aulie, suggests a causal connection between the two events:

The place of al-Ghazali in the rise of modern science is distinct and of consequence. It lies in his opposition to major portions of Aristotelian thought and that by means of his theistic affirmation of creation. For him, creation meant a coming into being; the creation was an expression of the divine will; for him, coming into being meant that the creation was separate from the creator. By his affirmation of creation and rejection of eternality he helped to lodge an ineluctable doubt at the heart of Aristotelian thought. ... [T]his affirmation of faith was bequeathed by Islam to Christianity in the later Middle Ages, to become integral to the rise of science during the Renaissance.

Richard P. Aulie, "Al-Ghazali Contra Aristotle: An Unforeseen Overture to Science In Eleventh-Century Baghdad". Perspectives on Science and Christian Faith vol. 45 (March 1994): 26-46.

It's completely anachronistic, not to mention philosophically dubious, to object to Ghazzālī's philosophy on the grounds that he gave too much weight to theology and divine revelation. One might as well object to Thomas Aquinas or Duns Scotus on these grounds. Like Aquinas and Scotus, Ghazzālī's intent was not to describe natural mechanisms, but to give an accurate account of human reason and its relationship to the world. His work is frequently compared to Descartes, although they have great differences over epistemology. He is also compared to Kant and Wittgenstein, namely:

While Ghazzālī does not state the issue in such terms, the fundamental mistake made by the philosophers is that they conflate the results of logical reasoning with empirical reality. Centuries before Wittgenstein, Ghazzālī argues that in doing so philosophy violates its own rules and trespasses on a domain over which it has no jurisdiction.

Koshul, "Ghazzālī, Ibn Rushd and Islam's Sojourn into Modernity"

One blogger named Ibrahim Arsalan has responded directly to Tyson, writing:

The dispute Al Ghazali would have with the philosophers and that Averroes would have with him [is] over the nature of Aristotlelian metaphysics, not the demonic nature of scientific thought. Such an attack on Al Ghazali by Tyson is laughable considering he furthered the development of secular methodology and would later be praised by European secular thinkers who Tyson is so eager to praise. Also, Tyson is in error when he says of Al Ghazali, “… out of his work, you get the philosophy that mathematics is the work of the Devil”. Al Ghazali actually called the sciences and mathematics of his day mamduh (praiseworthy) adding, “…because of their absence, the community would be reduced to narrow straits.”

You can learn more about Ghazzālī on this podcast: History of Philosophy without any gaps. That podcast also covers the full spectrum of Islamic philosophy in his time and after him.

Answer 2

Ghazali actually praised the disciplines of math and science saying they are necessary to a prosperous society.

Sciences whose knowledge is deemed fard kifayah comprise [all] sciences which are indispensable for the welfare of this world such as: medicine which is necessary for the life of the body, arithmetic for daily transactions and the divisions of legacies and inheritances, as well as others besides. These are the sciences which, because of their absence, the community would be reduced to narrow straits

I challenged Tyson's assertion in my blog post Fact Checking Neil deGrasse Tyson.

And Tyson responded:

As for Al Ghazali, a more accurate representation of his views is that the manipulation of numbers was an earthly rather than a divine pursuit. And it was divine thoughts and conduct that were widely promoted -- to the exclusion of earthly conduct. Earthly conduct became associated with being anti-God, which I characterized as the devil. In later speeches (over the past year or so) I leave it as a simple split between earthly and divine pursuits, realizing that I was misleading some people by mentioning the devil at all.

(Emphasis added by me). I would say he misled anyone who believed what he said.

The beginning to Tyson's talk on the Islamic Golden Age was a false account of Bush's 9-11 speech. According to Tyson Bush attempted to "distinguish we from they" within a week of the twin towers disaster. Exploiting that extremely emotional time to sow division would have been a despicable thing to do. But Bush's actual speech was a call for tolerance and inclusion, exactly the opposite of xenophobic demagogue Tyson portrayed. Tyson eventually admitted his account was the result of poor memory and conflating Bush's eulogy for the Space Shuttle Columbia astronauts and his 9-11 speech. See this Washington Post column by Jonathan Adler. As Adler notes Bush didn't attempt to "distinguish we from they" in either speech.

Neither did Islamic innovation end in the 12th century with Ghazali. See this list of Islamic scientists. Abu A-Hasan, the father of symbolic algebra, was born three centuries after Ghazali's death.

Tyson delivered this talk to many skeptic gatherings from 2006 to 2014. Then in 2014 Sean Davis called out Tyson's account of Bush's 9-11 speech. Islamic scholars had been calling out Tyson's inaccurate statements on Ghazali. But it has been only recently a wider audience has been paying attention to these criticisms.

It is instructive that for years Tyson would deliver these false stories in the presence of folks like Lawrence Krauss, Michael Shermer, Sam Harris and other prominent skeptics. His audience received these stories with enthusiastic applause. It seems they accepted these false stories without question. Which demonstrates even self proclaimed skeptics can swallow falsehoods if they seem to confirm their favorite prejudices.