Usually we think about presence as a noun -- it's something that you either have or you don't. Right? Oh, that actor has so much presence. It's a noun. Leslie does not necessarily agree with this! He thinks that we can transform it into a verb so that presence becomes something you "do" not something you "have."
This is a skill that an actor builds. It's not inherent or innate. And it must be made anew each time. Leslie talked about presence in terms of foreground and background noise. The noise keeps us from being present and it never stops. Developing presence as a skill involves making what is in the foreground more vivid, and the background less so. Athletes are very good at this. Musicians are pretty good at this. Actors ... not so good at it. (Improv actors get pretty good at it.) Most actors are not so good at dealing with fixed things.
And this is what we are working with as actors -- fixed things, like scripts and blocking. But if the present is rooted (that is, newly rooted) from moment to moment, how do we work backwards? We must listen. All great acting teachers will tell you that. Even when you are speaking a long speech, you must listen. Presence is more in listening than in speaking. Remember, even long speeches are persuasive arguments, never description, so someone else is always present with you.
To relate this back to a few other posts ... I will fill in this "you" -- the audience.
And to relate it back to Delsarte ... being authentic is being able to say "now." Expressing here (Leslie rubbed his heart), not here (Leslie touched his head). We must feel. Now.
Reidel, Leslie. Personal interview. 20 November 2010.