Decadence is natural. All things of this universe decay, subject to the Second Law of Thermodynamics and the inescapable process of entropy.
Classical authors accepted decay as a natural condition of the world, and certainly of human society. The last books of Plato’s Republic—usually considered a work of political utopianism—are devoted to describing an apparently inescapable process of decay, from the regime of near perfection to the most vicious form of tyranny. The course of the world is to run down. The failure of one generation to pass along its virtues is akin to the natural degradation of our genetic code and the inevitable decline and death of our bodies.
The counsel of the classical authors was to delay the decay. Preserve the virtues; slow the rot; avoid unnecessary innovation. This counsel is at the heart of the conservative disposition: the world is arrayed toward decline, not progress; and, as such, the main role of a healthy society is to stave off decay through prudent maintenance of decent and sustainable social practices. Edmund Burke and Alexis de Tocqueville were among the modern heirs of the classical tradition, albeit anomalies in an age that considered itself enlightened and sought to overthrow the old ways in favor of progress.