The experimental setup of the self-referential quantum measurement, jovially
known as the "quantum suicide" or the "quantum Russian roulette" is analyzed
from the point of view of the Principal Principle of David Lewis. It is shown
that the apparent violation of this principle--relating objective probabilities
and subjective chance--in this type of thought experiment is just an illusion
due to the usage of some terms and concepts ill-defined in the quantum context.
We conclude that even in the case that Everett's (or some other "no-collapse")
theory is a correct description of reality, we can coherently believe in
equating subjective credence with objective chance in quantum-mechanical
experiments. This is in agreement with results of the research on personal
identity in the quantum context by Parfit and Tappenden.Comment: 9 page
