  According to QBism, quantum states, unitary evolutions, and measurement
operators are all understood as personal judgments of the agent using the
formalism. Meanwhile, quantum measurement outcomes are understood as the
personal experiences of the same agent. Wigner's conundrum of the friend, in
which two agents ostensibly have different accounts of whether or not there is
a measurement outcome, thus poses no paradox for QBism. Indeed the resolution
of Wigner's original thought experiment was central to the development of QBist
thinking. The focus of this paper concerns two very instructive modifications
to Wigner's puzzle: One, a recent no-go theorem by Frauchiger and Renner, and
the other a thought experiment by Baumann and Brukner. We show that the
paradoxical features emphasized in these works disappear once both friend and
Wigner are understood as agents on an equal footing with regard to their
individual uses of quantum theory. Wigner's action on his friend then becomes,
from the friend's perspective, an action the friend takes on Wigner. Our
analysis rests on a kind of quantum Copernican principle: When two agents take
actions on each other, each agent has a dual role as a physical system for the
other agent. No user of quantum theory is more privileged than any other. In
contrast to the sentiment of Wigner's original paper, neither agent should be
considered as in "suspended animation." In this light, QBism brings an entirely
new perspective to understanding Wigner's friend thought experiments.
