=+The idea is that an observer with the information in $ (but ignorant of w itself) in principle knows the values p( A, «) because each p( A, . ) is measur-

able . If he has the appropriate randomization device, he can draw an «'

from 0 according to the probability measure p( ., w), and his w' will have the same distribution Q. = P. that w has. Thus, whatever the value of the unknown 0, the observer can on the basis of the information in $ alone, and without knowing w itself, construct a probabilistic replica of w.