text:  But while we accept this explanation and are grateful for the deliverance it works for us we must also admit (and we are not aware that Mr Mill would controvert this admission ) that there is a large class of cases in which our reasoning betrays no reference to this anterior experience and where the usual explanation given by teachers of logic is perfectly applicable; cases where our object is not the discovery of truth for ourselves but to convince another of his error by showing him that the proposition which in his blindness or prejudice he has chosen to contradict is part and parcel of some other proposition to which he has given and is at all times ready to give his acquiescence