Religion and Reason are two different things! Religion's genesis is God, Reason's is human. While Religion, by definition, is superhuman, the epistemology of Reason springs from the instinctual ability of humans to ponder and contemplate the universe and what's in it - Reaon's tames itself by subjecting its secretions to certain procedural ways of looking and thinking. Religion is God's blueprint to the rightful human conduct, which, in essence, beyond human capacity and/or ability to ascertain the premises (on which it's based) and its finalities! Are Religion and Reason compatible? Both have recourse to basic assumptions: Reason's basic assumption knows no confinements and leaves the mind to roam freely, while Religion's bound by the foundational premises or tenets. Logic is the procedural tool of the first, Belief is the demand of the second. Belief springs from the intuitive pre-logic imaginative instinct, Logic is an acquired ability of the human mind to manage its own outputs. The apex of Reason is Science, the nadir of Religion is Dogma. As to compatibility, in stricto senso, there's none. Religion and Science are irreconcilable, though, both partake in intuition and imagination, thus intersect in the human mind, the only communal locus where the impossible verges on the possible! They're bound to rub shoulders with each other, at least in the short and medium ranges, since cohabiting in the same space. They become mutually exclusive only when they're set to compete to the same truths. Complementarity leaves wiggle room for both to pursue their agendas without getting in each other's way. Only in this sense Einstein's often quoted saying: "Science without religion is lame, religion without science is blind," may find some justifications.
The problem with setting Religion and Reason in the same breath is complex and sometimes misleading. At the face of it Religion can be subsumed as a category of the human mind's production, that's, part of human Reason disguised under God's workings, however such an extension may strengthen the fact of the fallibility of Reason. The Misleading part resides in the cul-de-sac human Reason conducts itself in, since Religion often pulls the rug from underneath its creator, Reason -just go back and read the ruinous campaign mounted by al-Ghazali against the edifice of reason , par excellence, Philosophy! As entangled in the mind as both are, this complexity is eased only through the modern condition of 'compartmentalizing', or the ability of human mind of carrying full load of disparate baggage contents without succumbing either under their weight or losing the sense of directions. That's, some sort of what's taking place in a modern library or museum, an internal organization and indexing (in the mind), in which seemingly incompatible categories and attributes find home side by side yet recognizable on their own. This can occur only if Reason is given the dominant role and charged with task to lead Culture. When this happens, while it's no marriage, a truce is instituted and a roommate type of existence is settled on.
Religion as the precursor, or the opening salvo, so to speak, never was comfortable with Reason. Actually for most of history Religion took as its primary task to suppress Reason. Blurred Reason working against itself! Religion and Reason went through ferocious wars the latest of which was the European Enlightenment and have survived the onslaught and havoc which their infightings brought to both. The result, at least, in those societies that have instituted and those that have accepted the Project of Modernity is a precarious and fragile balance, where both live side by side, granted each adheres to the non-encroachment on the territory of the other. A detente of sorts between God's fixed dictates and human ever shifting winds. That's when Religion accepts to play the role as a guide-post, a beacon if you will, and the anchor of last resort, Reason may live with such an arrangement, so it can navigate the uncharted oceans without the nagging danger of losing it, getting lost and going astray!
Reason cannot reform Religion, nor Religion can stop -it may slows it down- Reason. Perhaps, because of the fact that Religion's teleology is circular, pent on itself, always ending where it's started; Reason, on the other hand, while gradual and accumulative, shoots its tentacles towards the "creative destruction". If there's any reason why Religion endures, it's, perhaps, the idea that it's possible to form a coherent view of the world. Reason may not exclude such a notion but it doesn't embrace it warmly either -no absolute certainty. In the maelstrom of Reason's ever changing turns and twists, Religion's steadfastness is an attribute of stability. Reason's sign posts are the mirages it gleans across the horizons matched only by religion's genetic makeup, that's, ambiguity and resilience. Reason's sought after lucidity is only reaction, or perhaps to compensate for the Sacred Texts as the epitomes of ambiguity rooted in the open-ended declamations. Thus, Texts may, theoretically, leave wiggle room for adaptability, history has shown any adaption to the mundane world tend to be exception, rather than the rule -mere cosmetic face surgery. The body is kept always intact! Critiques from within or without tend to stiffen its adherents to further orthodoxy. The few Religions's convolutions may have started from within but always spun in centrifugal directions to without, and ended up in more divisions and multiplications of the same cells yet a bit different from the original stem cells. Factionalism and sectarianism, mysticism, sufism, etc. were the outcomes of such forces. Eastern and Western, Protestant and catholic Christianities, Orthodoxists and Reconstructionits in Judaism, Sunnism and Shiism in Islam, etc....
Critiques never worked within Religions. Negative thought tends to be looked at, if not as a passing fad, an insidious sinkhole with potential domino effect. Only positive statements, that's, an alternative practice, seem to shake a bit the establishment's self-imposed stasis. That's the way reformists went about the business of changing somewhat what they thought needs to be changed. Rather than correct few things from within or urge the discard of others altogether, a modus vivendi was sought where the two versions could compete. Martin Luther had to nail his 95-Theses on the door of Wittenberg Church before the Catholic Church took notice and the Protestant and Reformation movements were set in motion. The same will probably happen with Islam. Only when a true reformist comes up with a whole positive scenario, an alternative praxis, will the drowsy multitude start taking sides and a reform movement will start to coalesce.
Religion, in its essence, addresses the individual - the individual's relationship with his/her Creator- and deals with the Extraordinary. Reason, on the other hand, deals with the mundane -that's the secular- on both social and individual scales. The two levels -sacred and mundane- may intersect but clearly separable. God and Caesar, may seem to be exclusive but they compliment each other, though each has special concerns and at times may appear to pursue his/her own limited goals. The discrepancy between the two resides in the often repeated aphorism: God may work in mysterious ways, but Reason's mainstay is transparency. Shadow versus penumbra -if not light! When the distance between them gets wider, as in Islamic cultures, it's filled in by the twilight zone . As gapstop and to bridge the chasm Secularism, secular humanism -the millennial knowledge and the wisdom of the centuries- came to answer the failure of the sacred to deal with the mundane and to save Man from oblivion. Since God's edicts are few and far in between to meet Life's tumultuous vicissitudes Secularism took the onus to where it belongs in the first place: Social Reality! The notion to put Law and Social Morality, as worldly concerns, out of the realm of whereabouts and ambiguities, and root them in the only realm where they originate and made use of was/is such a revolutionary breakthrough, an irruption!, that it truly changed the face of the earth since its adoption. Social contracts, political institutions, civil society, etc. were/are the brainchild of such a volcano.