What type of figurative language is this?

To a degree academic freedom is a reality today because Socrates practiced civil disobedience.

It is an allusion

Explanation:

An allusion is a figure of speech that provides a brief and indirect reference to something (like a phrase, a place, idea or a literary work) or someone that is commonly known and that is significant in our society.

This excerpt is an example of an illusion because it provides an indirect and brief reference to one of the greatest ancient Greek philosophers: Socrates.

This is an example of an allusion, because the sentence is referring to an important political personality of the past (Sokrates). The writer wants to underline the importance of Socrates's contribution to the academic freedom.

An allusion is a type of figurative language which uses a reference to a significant person, thing or event, real or fictional, in order to make a statement stronger. It usually establishes a comparison so that the readers understand better the main idea.