The epistemic limits of shared reasons

Accounts of public reason disagree as to the conditions a reason must meet in order to qualify as public. On one prominent account, a reason is public if, and only if, it is shareable between citizens. The shareability account, I argue, relies on an implausibly demanding assumption regarding the epistemic capabilities of citizens. When more plausible, limited, epistemic capabilities are taken into consideration, the shareability account becomes self-defeating. Under more limited epistemic conditions, few, if any, reasons will be shareable between all reasonable citizens, making the shareability account so demanding that it precludes public reasoning altogether.