For the actor, sincerity is not a moral issue, but instead a practical application, an essential function, to be trained and exercised, as with any other muscle.
I remember I first was directly confronted by this word “sincerity” in the writings of Barrault. He left no doubt as to its fundamental importance in the theatre. It has ever since been an important word in my professional vocabulary.
Interestingly, the word doesn’t translate smoothly into some languages, for instance Danish, which suggests that there is a cultural component. It carries a sense of “authenticity,” with “artificial” being a close opposite. There is a sense of deep commitment to an action or statement, to stand by one's intentions. It certainly doesn't mean humourless, or without style, and should not be equated with naturalistic acting. Naturalistic acting however does have a special relationship to sincerity, in that it leaves the sincerity muscle relatively exposed. For this reason, naturalistic acting has an important place in an actor's education. Although as Lecoq once pointed out, if you concentrate on naturalistic acting when in your twenties, you risk being a very boring actor in your forties!
I don’t remember Lecoq ever making sincerity a big issue. I think he covered it in his own way with terms like “gratuit” (cheap, too easy, unsupported), “disponible” (open to what’s really there) and “appui” (solid intentions require a solid grip on a solid physical base). His choice to work with honest, naïve styles in which the characters have few hidden agendas, his rejection of conscious cleverness, and his promotion of physical imagination over psychological solutions, all nudged the student in the direction of a natural sincerity.
One of the most misguided and confusing things you can ask an actor to do is be "true." It is not her job to replicate. It is not her job to establish a moral standard. But you can ask her to exercise her sincerity muscle, to defend through the action not only the character she is playing but the way in which she transforms reality.
When I work with second year students at the Danish National School of the Performing Arts, they have already had many months of intensive technical training. I challenge them to bridge the gap between sincerity and expression, to experiment with exploiting the absolute limits of their newly developed physical and vocal technique while still remaining sincere. There is no such thing as "over acting," only "under supporting" with a weak sincerity muscle.
The key to your own sincerity lies in the other actor. It is there when you feel it is important to change that person, and it is there when you can allow you yourself to be changed. You will find it when you allow your partner on the stage to be a living human being and not just an object, not just another piece of stage furniture that returns lines. Insincere actors resemble the conventional definition of Asperger’s syndrome, experiencing other people as things.
Sincerity is like neutrality, in that it is not a final, achievable state, but rather a direction in which to travel. How far you have travelled is up to the audience to decide, and different audiences will have different opinions. If your work can convince me, then of course you are sincere, why say otherwise? Or is it actually the work that is sincere, not the person? Ultimately it is not the actor's job to do what feels sincere, but what looks and sounds sincere. The audience is the measure.
The Stanislavski tradition seems to start with sincerity and move towards expression.
The Copeau tradition seems to start with expression and move towards sincerity.
The Stanislavski tradition seems to say: “Tell no lies and your body will follow.”
The Copeau tradition seems to say: “Trust your body and you will tell no lies.”
Both can be right.
Sincerity is the actor’s Zen, because as soon as you are thinking about it you lose it.