 Fourth, it might seem that public reason cannot successfully abstain from some claims about moral or political truth. In order to explain why we ought to accept a principle of public reason or public justification, we cannot simply say it ought to be accepted because the principle itself can be publicly justified. Such a claim might be trivially true—its truth established by restricting the constituency of public reason to those who endorse the idea of public reason—but this does not vindicate the principle, nor does it distinguish a principle of public reason from similarly “insular” principles that appear clearly dubious, for example, a principle mandating that moral principles are valid only when endorsed by Albert, who also happens to endorse this principle granting him exclusive moral authority (Estlund 1998).