This, in short, is Franz Rosenthal's thesis, a hypothesis the German-born US orientalist developed into a classic tome devoted to the study of Islamic civilisation and which, despite its year of publication, still remains relevant today.
The idea of studying the conceptual bases of a civilisation is certainly original, but it is also risky because of the sheer size of the topic, the always recurrent temptation of defining it once and for all and the difficulty of transposing the results from the reading of texts into a conceptual framework that is alien to them.
Despite these dangers, of which the author is well aware, Rosenthal stresses ad abundatiam the importance of "knowledge" as a concept in every field of Muslim civilisation, from the Qur'an to religious studies, from Sufism to philosophy, not to mention adab encyclopaedias and pedagogical literature.
Although the panoply of sources cited (some hand-written) can create an impression that Rosenthal is a know-it-all for, that is not the case (in dialectical theology for instance) for he does slide into oversimplifications here and there. And yet in his defence he would probably say that had he not resigned himself to sliding a bit from the start he would not have come up with any overall picture. Indeed notwithstanding any one point, his original intuition remains valid, namely that classical Muslim civilisation was moved by an unconditional assertion of the superiority of knowledge over all other human activity.
But what is the relationship between Knowledge with the capital letter and any particular forms of knowledge? For Rosenthal practitioners, whatever their field, show a tendency to see "Knowledge" as an absolute, the more so in the field of religious studies.
When he studies doubt he shows the other side of the coin in this unending search for truth, namely that "Knowledge not affected by doubt was passionately believed to be within the easy reach of every believer. What this meant for the history of knowledge in Muslim society need not be spelled out for the modern Western observer" (p. 308).
In his conclusions Rosenthal asked what it meant for a civilisation, and human history as a whole, to have knowledge as its main concern. In the end he did not find the answer but we owe it to him to have raised the question, identified some paths for further research and provided the first elements of a possible answer.