An actor uses his body as a tool and an instrument. In the same way a musician plays an instrument, the actor uses his body to convey feeling and emotion. An animator uses a pencil or a computer to create the same thing, the same exact way... An actor is taking words that are not his own, and he has to bring some kind of authentic life to those words. It's the same goal, to create this authentic life. Even if it's a drawing, or if it's a cartoon, you're still trying to create authenticity because, if the character emotes authentically, it has a power to connect with the audience.