"It is the principle of the decision by which we are bound, not a mere rule that in exactly the same circumstances we are to arrive at the same conclusions. Therefore to say that the decisions are wrong in point of principle, if that principle was clearly laid down, does not relieve us from the obligation of following the principle of the decision, because the whole theory of our system is, that the decision of a superior Court is binding on an inferior Court and on a Court of co-ordinate jurisdiction, in so far as it is a statement of the law which the Court is bound to accept."