Sometimes people have problems with the final stage of lovingkindness practice — developing goodwill for all beings. Because how can you possibly relate to all beings! It’s impossible!
I think the language of “all beings” can be misleading. We can’t literally have metta for all beings because we don’t know who they are, or where they are, or even if they are!
The final stage is called, in the commentaries, “breaking the bounds” and I see it as breaking the bounds of one-to-one relationships. The middle three stages all include a one-to-one relationship with someone: a friend, a neutral person, and someone you have difficulty with. A visual comparison (not that I’m saying it has to be visualized this way, or visualized at all) would be a ray of light going from you to that person. But in the final stage, at least the way I experience it now, after many years of evolution in my practice, I drop the sense of one-to-one relationships altogether.
What I do, in essence, is simply to have a sense that my mind is imbued with lovingkindness, so that whoever I call to mind, or whoever is physically in my presence, is touched by a mind of lovingkindness. So a visual comparison here would be light radiating out from us in every direction. Whoever enters the range of the light is touched by it. Again, I don’t actually visualize light at all in my meditation, I’m just trying to find a metaphor to illustrate the difference between metta “bounded” by a one-to-one relationship and metta that has “broken the bounds” and that is simply part of our awareness, touching whoever enters that awareness.
How I’ll enter the final stage is to become aware of the space around me, including the light and sound on all sides, simultaneously. My awareness now feels spacious: I’m conscious of a field of awareness that in a sense expands all around me. And I’ll have a sense of letting that field of awareness be filled with lovingkindness. I’m doing that now as I type. Shantikirika and Eric are in the office with me, one to the left and one to the right. I am aware of their presence, and I’m doing that with a gentle “touch.” If I could hear the guys in the office upstairs, I’d be doing the same with them, although they’re unusually quiet this morning. And then I call to mind myself, the friend, the neutral person, and the person I have difficulty with, and rather than “send” them metta I simply receive them in a loving awareness. And from there I can call to mind various people and places, and similarly let them be touched by the light and warmth of my mettaful consciousness.
In in principle, all beings are touched by my lovingkindness, in the sense that whoever enters my mind is met with love. But I don’t have to literally imagine “all beings.” Thank goodness!