Now if all possible transfers commonly occurred it
would have been a lmost impossible to construct useful
t heories. Nevertholess, such t heories wore pa.rt of our
ev~rydo.y discussions. rrhis was becau60 it was being
tacit ly assumed t hat certain t ransfers could not occur.
lt occurred to me t hat it wou ld be wi Re to stnte t hese
preconceptions explicit ly.