  Bayesian probability theory is used to analyze the oft-made assumption that
humans are typical observers in the universe. Some theoretical calculations
make the {\it selection fallacy} that we are randomly chosen from a class of
objects by some physical process, despite the absence of any evidence for such
a process, or any observational evidence favoring our typicality. It is
possible to favor theories in which we are typical by appropriately choosing
their prior probabilities, but such assumptions should be made explicit to
avoid confusion.
