I hold an often ridiculed view that the scene the actor is playing can impress upon the his mindset. I don't mean that actor “becomes” the character – this is nonsense – I mean that the scene can influence the actor, for example: if the actor discerns in his analysis that the character he is playing doesn't care about what is happening in the scene, it may become that the actor stops caring about the production he is working on. Please note: the actor cannot know this influencing is taking place, it happens gradually, almost imperceptibly, and the actor will blame his eventual change of mindset on everything except the real cause: the scene itself.
However, for the organic actor, this influencing is positive and creative, even if it is unconscious. If for example he is playing a scene where the character is bluffing, all kinds of wonderful, little, provocative moments may reveal themselves in performance, small tells (eg – playing with an earlobe, or handling pieces of paper), which are unplanned, infact, could not have been planned, but there they are, fabulously expressive, complex, intense, and true. The actor doesn't want to consciously re-create these great moments - they're great because they're spontaneous. The actor may try to re-create them because he cherishes them, and further, they represent strong work and so it makes sense to recreate them, but the actor must resist this temptation and create afresh each time. Any re-created version of them will be a dead thing – that moment has passed, move on.
The alternative to the organic actor is the presentational actor, who frees himself from the hassle of creation by mapping out his entire performance: every gesture, every turn of the head, every inflection, has been planned in advance (and labelled “characterization”) and the performance is merely a plodding implementation of the plan, even to the extent that changes to his scene partner's performance are ignored. The object of presentational performance is to control everything in order to avoid the terror of facing up to the truth of the moment (which can seem like an abyss). Presentational acting has got nothing whatever to do with creating, and everything to do with limiting criticism, it's rarely provocative or exciting in it's search for bland flawlessness. Furthermore, this actor plays everything in inverted commas as it were, indicating to the audience that he isn't really the character (because of course we couldn't discern that for ourselves – doesn't this actor know that his performance is an illusion which the audience willingly buys into?), and would show that the character is bluffing by using a predetermined general physical nervousness, flicking the eyes, and other cliches, rather than letting the performance manifest itself by confronting the moment. The performance of the organic actor however, appears not to be performance at all, but simply the functioning of his personality, indeed, no differential between his work and his personality can be made.
It takes courage and strength to face upto the truth, it is far easier to brush it under the carpet, and trot around in a bland hypocrisy. Acting is not about being perfect all the time, although yes, we need to strive for excellence. The moment may not be perfect, it may not be how we intended it, but it may be true, and this truth is always provocative, always thrilling, always beautiful.