Today, “empathy.” Some stress empathy is central to success in character portrayal. That is, the actor puts himself in the shoes of another, sees that person’s point of view, and, with compassion thus engendered, demonstrates a portrayal of that “otherness” in himself.
But a character is not a person. A role is not a human being. It is a fiction in the mind of the writer. My job and your job, as a character actor, is not to “reflect humanity.” (A reflection is backwards, by the way.)
Rather, it is to enact a fiction. The world of that fiction is described and circumscribed by its dialog and its stage directions. It is a world complete (if well written) in itself.
The characters in the staged world do not need to comport with one’s own experience in life. An Artistic Director once said to a playwright I know of his play, “No one speaks like that.” A comment which demonstrates that A.D.’s profound failure of theatrical imagination. It is not that no one in THIS world speaks like that, but every character in the FICTIONAL world of that work does
Similarly, an actor does not have to demonstrate a compassionate concern for the life of a fictional character. Rather, he invents by means of his imagination, rooted entirely in the text, a character that believable within the fictional world. Whether or not this character is believeble in life is immaterial. The offstage world has no reality for the characters onstage.