A student of philosophy is walking alongside their philosophy tutor, when the tutor sees two people arguing. They are at the top of their respective houses leaning out of the windows. The houses are jettied out over the street, so that the two can easily hear each other.
The philosopher pauses and says to the student, “Those two will never agree.”
The student listens more carefully to the two people arguing, they do seem to be thoroughly enjoying their row. The student knows that this will not be enough reason to satisfy the tutor; as a philosopher they will want a more logical reason. The student has to confess that they do not know why the two people arguing will never agree.
The philosopher looks kindly at the student.
“They can never agree. Since they are arguing from different premises.”