ON ACTING: The Danger of Solitary Rehearsal
So by the time we enter performance, we are operating as if in a glass bell jar. We know in advance what we are going to say, and we know how we are going to respond the other characters….irrespective of the actual ensuing reality of the living, vital other persons on stage or on set with us at the time; we are acting not with that other real persons-as-characters, but with straw dogs of our own solo-rehearsed or self-rehearsed making.
The other actor in the real performance scene has by now has become a figment of our imagination, not the living, shifting breathing spontaneous person in front of us. Rather s/he is some imagined personage from our rehearsal, a straw dog to deal with as we predetermined.
The other actor could be any actor in the cast or even off the street. It doesn't matter to the locked-into-rehearsal bad actor; s/he would still act and react to them in performance all the same!
Love rehearsal; but beware of it. See rehearsal as a planned set of desired possibilities; not permanent choices set in stone. Reality (in performance) must always trump planned expectations; as it does in life...which is what we are trying to create on stage.