This project resides at the intersection of social epistemology and Islamic history. The epistemic conditions that make statements like ‘Group A believes p’ true are central to social epistemology. Current literature, however, does not adequately consider the epistemic significance of reasonable peer disagreement on belief attributions to religious communities. This paper defends an account of sustained reasonable peer disagreement, shows its epistemic significance for belief states of collective agents, and makes a strong claim concerning how we should understand the doctrinal boundaries of religions. To begin, I ask you to consider that evidence and reasoning are not synonymous in the way that internalist views of justification claim, nor are externalist views wholly adequate. I suggest that the internalist-externalist problem resides in an equivocation between justification and reasonableness. When we separate these, reasonable disagreement appears epistemically permissible, because attributions of reasonableness track the fittingness of beliefs to internal mental states (memories, perception, background belief); whereas justification tracks truth – fittingness of beliefs to subjective, individual epistemic criteria and objective, shared epistemic criteria. Given this distinction between justified and reasonable beliefs, it is at least plausible that I could reasonably (and justifiably) believe p and simultaneously believe that you, my epistemic peer with respect to p, reasonably believe ~p. Given a plausible theory of reasonable peer disagreement and that belief attributions to religious groups are often grounds for political or civil strife, an adequate epistemology of intra-religious disagreement can motivate epistemic humility and fend off conflict. Also, figuring out what groups actually believe seems an essential and prior question to meaningful religious discourse. Consider the implication of intra-religious peer disagreement on the truth value of belief attributions to propositions of the kind ‘Islam believes (or disbelieves) x’ where ‘x’ represents any statement that Muslims purportedly collectively believe (or disbelieve). Many religious tenets, including the one exhorting Muslim women to cover their hair, are based on scriptural inferences and are informed by subjective background information without shared or objective epistemic principles to determine which reasoning is stronger. Thus, employing exegetical and hermeneutical methodologies to determine the truth of such claims is not adequate to the task because of the sheer volume and diversity of sources and conflicting authorities. Thus, in the absence of objective epistemic principles, parties to the peer disagreement should reasonably disagree and the belief attribution to the group remains undefined – neither true nor false.