 There is a common difficulty underlying all the untenable alternatives Kant considers. They look for substantive guidance from outside of reason itself—just as hypothetical imperatives only guide action if some end is taken for granted. Kant calls this heteronomy—that is, reasoning directed from the outside, by an authority that is merely assumed or imposed. The problem is to find ways of acting and thinking that are authoritative—that is, are entitled to guide everyone’s acting and thinking. To gain this entitlement, they must be autonomous—that is, not dependent on an authority that itself refuses justification.