All that is human must retrograde if it do not advance.

Gibbon’s aphorism frames human affairs—individual character, institutions, and civilizations—as subject to a dynamic law: stasis is illusory. If people or societies do not actively cultivate improvement (in knowledge, virtue, governance, or discipline), they will not merely remain unchanged; they will slide backward through neglect, corruption, or entropy. The line reflects an Enlightenment-inflected belief in progress while also echoing Gibbon’s historical sensibility that decline often comes less from sudden catastrophe than from gradual relaxation of standards and loss of civic energy. It is frequently invoked as a warning that maintenance requires effort and that progress must be continually renewed.