Muslims are taught by tradition to refrain from using reason in religion. The use of reason is associated with the expression of "capricious opinion." The bias against reason is also based on the perception that the use of reason in Islam is kufr. This is known as al-fiqr kufr. Refraining from reasoning, however, makes it harder to understand and therefore follow revelation. Belittling reasoning defies the teaching of revelation, too. Moreover, the failure to think of the effects of our actions may result in extremism. Extremists are unreasonable. Refraining from the use of reason makes it difficult to understand revelation, or anything else for that matter. From a sharia perspective, refraining from the use of reason takes us from the ranks of the mukallafun, or accountable persons. Is the work of the ulema that refrain from reasoning reliable? Muslims reminisce about the achievements of the past. Much research emphasizes past successes, "what Muslims had first." Few ask what went wrong, preferring to entrust the responsibility for this research to non-Muslims. But non-Muslims are not necessarily unbiased. Due to the insufficient use of reason on the relationship between reason and revelation, Muslims embraced the perception that there is an adversarial rather than a symbiotic relationship between reason and revelation. The rejection of reason enabled the emergence of traditional Islam, the acceptance of the teaching of abrogation, and the belief in predestination. The belief in predestination rests on the rejection of causation. The aversion to reasoning resulted in aberrations in exegesis and jurisprudence. Thus, traditional exegesis and jurisprudence require re-construction, this time on firm foundations. This requires the rehabilitation and re-engagement of reason, the restoration of revelation to its preeminence in relation to tradition, rejection of problematic presuppositions regarding revelation, and dispensing with the teachings of abrogation, fatalism and aggressive jihad. Taqlid resulted from the shutting of the gates to reasoning or ijtihad. Anti-rationalism produced two strands of Islam: traditional and political Islam. Both stem from the rejection of reason, the unquestioning following of tradition and the engagement of the teaching of abrogation. Traditional Islam was evolved to keep the peace by sedating the believers with the teaching of predestination. Political Islam was engineered to provide religious justification for waging wars of aggression in the garb of spreading Islam by the sword. The rejection of reason resulted in a corruption of the method of interpreting revelation. The religious sciences, including exegesis and jurisprudence, became irrational. For that reason they could not generate reliable results. The emergence of traditional Islam was enabled by the eclipse of revelation by tradition. The emergence of political Islam was enabled by the abrogation of the peace verses by the verse of the sword. The transformation of Islam into its traditional and political variants was enabled by recourse to the teaching of abrogation. It was also buttressed by the perception, alien to revelation, that the world is separated into two areas, the realm of peace (dar al-Islam) and the realm of war (dar al-harb). It is necessary to rehabilitate and reconstruct knowledge, which was tarnished by the rejection of reason, and ensure that all religious sciences rest on reliable foundations.