As mentioned on the podcast, our original intention was to cover Zen, but that seemed difficult without covering some of the history. Nagarjuna was a big influence on Zen, particularly in the "Reasoning" reading where he urges disassociation from even Buddhist doctrine itself, i.e. the transcendence of all views. That's the kind of mind-bending apparent self-contradiction that Zen is famous for.
Here's a quick clip of Nyogen Yeo Roshi talking about the illusory nature of the self and your experienced world:
Roshi here tells us to appreciate the beauty of the illusory world; we just don't want to get stuck in it. He argues that the present is an illusion because it's temporary, because the passing of time makes all events past unreal, because they can't be produced for reexamination in their fullness. (I don't find this particular point convincing in the least, myself.)
How do we bring the masses to enlightenment? We have to see that there really aren't any masses that need enlightenment. We have to see that we aren't really separated from everyone else, that we contain the whole. Now, this latter mystical sentiment isn't one we saw specifically in Nagarjuna: the self is an illusion, but realizing emptiness doesn't mean that we instead identify our self with the whole.
An influential figure in American Zen is the author Ken Wilber. In this video, Wilber refers to a "fundamental, authentic transpersonal self."
If we suspend belief in the existence (or even identification, apparently) of objects of experience, we are still left with "I amness." Somehow if we reflect on our past experience and the continuity between now and five hours ago, then we're supposed to conclude that this "I amness" was present even before my birth, which patently doesn't follow, nor does it even follow that because my thinking of the explicit recognition of my ego (i.e. self-consciousness) on past occasions that I was always self-aware.
On the contrary, it's highly in dispute in the philosophical literature whether all consciousness is in any sense self-consciousness. It's just that if we look back at a time when we were, e.g. really engaged in some activity and not thinking of ourselves, we first of all can't really recreate that experience to determine whether there was a sense of self there (so we could impute self-consciousness when there wasn't any), and second, the experiences where we were self-reflective will be the easiest to remember, as self-consciousness involves exactly the kind of rehearsal (it's like you're living the moment twice, both by experiencing it and thinking "I'm experiencing this," in effect taking notes on it).
As much as I can tell from some quick web research (and I welcome your corrections on this point), this "big self" idea came into Buddhism as part of the Mahayana tradition near the same time as Nagarjuna after the 2nd century A.D., but as usual historians are not sure about the date. It seems to be part of the Tathāgatagarbha tradition, with its chief text being the "Nirvana Sutra," and the idea is that we have both a conventional self and a Buddha self within us, where the Buddha self is that part of the Buddha that is identified with the whole of existence (recall Erik's comment on the podcast about the Buddha being unable to escape permanently from the world on ontological grounds: we're all fundamentally one, so unless we all go, he can't go either), so if we strip away the emptiness of the conventional self, what we're left with is not nothingness; in fact, what we've removed is our separation from everything.
I'm certainly interested in these potential shifts in identity and in mysticism in general, but as I'm sure I'll say many times when this comes up, if you have some mystical experience and become identical with the whole of creation, then when you come out of that, you should be able to tell me, for instance, how much money I have in my wallet, given that you were right in there hanging with my money as well as everywhere else in creation. Unless you can do that, then I'm not going to believe that you were literally infinite.