  We analyse a proposition which considers quantum theory as a mere tool for
calculating probabilities for sequences of outcomes of observations made by an
Observer, who him/herself remains outside the scope of the theory. Predictions
are possible, provided a sequence includes at least two such observations.
Complex valued probability amplitudes, each defined for an entire sequence of
outcomes, are attributed to Observer's reasoning, and the problem of wave
function's collapse is dismissed as a purely semantic one. Our examples include
quantum "weak values", and a simplified version of the "delayed quantum
eraser".
