An instruction is the commoner and more general and simpler expression, from which a commonplace is derived; for the instruction [is] a beginning of a commonplace just as the commonplace [is] of an attack. Such an instruction is something expressed thus, that it is necessary to begin an attack [on an opponent's contention] on the basis of the opposing coordinate assertions, but it is a commonplace if the contrary position is often opposed to the contrary, or if the contrary turns out to be the contrary to the contrary;[1] and again, as is one of the coordinate assertions, so are the rest. For a commonplace is now a kind of protasis derived from the instruction.