"Oligarchy is the first step toward dictatorship."

It is part of a cycle, described by Plato.

Aristocracy (Greek: "rule by the best") is degraded and becomes timocracy, timocracy is degraded and becomes oligarchy, oligarchy is degraded and becomes democracy, democracy commits suicide and leads to dictatorship, once the dictatorship is degraded the best members of society are moved to action and establish an aristocracy again.

I am here using the term Aristocracy in the original sense. "Hereditary aristocracy" is a contradiction in terms, as aristocracy seldom remains hereditary past two, and never beyond three generations.

How does one identify the "first step" in a cycle?