As usual, I've no time to say what I want to say, but here are some quotes from an article about Wheeler in Scientific American:
Wheeler was one of the first prominent physicists seriously to propose that reality might not be a wholly physical phenomenon. In some sense, Wheeler suggested, reality grows out of the act of observation and thus consciousness itself: it is “participatory.”
What is reality, then? Wheeler answers his own question with the koanlike phrase “it from bit.” Wheeler explains the phrase as follows: “Every it—every particle, every field of force, even the spacetime continuum itself—derives its function, its meaning, its very existence entirely—even if in some contexts indirectly—from the apparatus-elicited answers to yes-or-no questions, binary choices, bits.”
(See an earlier post).
But, while I'm typing, let me - arrogantly - add a comment on another paragraph from this article:
These ruminations helped to inspire two of the odder notions of modern physics. In 1957 Hugh Everett III of Princeton, in a Ph.D. thesis supervised by Wheeler, proposed the many—worlds theory: although we can observe a particle in only a single position, it actually occupies all the positions allowed it by quantum theory—in different universes. Four years later another Princeton physicist, Robert H. Dicke, introduced the anthropic principle: it asserts that the universe is the way it is because if it were not, we would not be here to observe it. Although many physicists. recoiled from such ideas as untestable and therefore unscientific, Wheeler urged that they be taken seriously.
I'm not at all convinced by the many-worlds theory. It seems somehow 'empty' to me: where does it take us? I'm with those who say it is un-testable and therefore not science.
On the other hand, the anthropic principle seems to me to be almost 'obvious' - and is why I'm baffled by some of the arguments that I've read recently which, if I'm understanding them correctly, seem to be requiring the universe to somehow have a high-probability of existing. Those arguments seem to be like a lottery-winner arguing that the probability of winning is so low if 20 million tickets are sold, there can't possibly have been that many tickets sold otherwise they would not have won. I won't buy a ticket because I know the probability of winning, at 20 million to 1, might as well be 0, but the lottery winner can't say that, because they have won. We exist, so we have won - and the probability of existing can be vanishingly small.