according to heraclitus, hegel and marx, the process that constantly moves and develops nature, society and thought with the conflict and overcoming of oppositions
for a more beautiful, happier, fairer, loving world; let this world sink for peace, for humanity. (see orhan gencebay)
summary is "everything also contains its opposite".
the thought system, which tries to destroy reality and the contradictions in this reality by dealing with it and trying to solve it, is known as the father of dialectic.
vi. from a sage, an ancient philosopher, who lived in bc china: "life and death come together; hard and easy, long and short, high and low ... all these coexist. sound and silence are one blend, before and after arrive at the same place together." (lao tzu, from "tao te ching")
a form of thought or action, which in ancient times means the art of reasoning soundly and correctly, in a more modern sense, based on contradictions.
in short, a nice anecdote about the dialectic of "everything also contains its opposite": they asked nasreddin hodja where is your nose, and the hodja showed his neck. oh, my teacher, they said, will the nose ever be on the back of the neck? hodja said that if you don't know the opposite of something, you can never know yourself.
simply put, it can be said that "rhetoric is for justification, for reaching dialectical truth". like the relationship between religion and science.