Thespis was the first actor.
The first person to step forward from the chorus and to speak as a lone voice, the solo voice, while the chorus looked on.
One from none.
What madness drove the man to remove himself from the safety of the crowd and to speak without their protection? Rather than the voice of the people; the voice of the individual, making a clear and present argument without the cover of the masses.
Soon the protagonist was joined by the deuteragonist and the tritagonist and even the antagonist. Individual voices, seperate from the chorus, making the case for humanity, for and against.
This is the great tradition that all actors in the present day stem from, that we owe our livelihood to, that we should aim to fufill every moment we are on that stage.
To be the voice that dared step out from the crowd, to stand up and be heard, to make the life or death case for the truth.