Or perhaps we ought not to understand the statement that the false conclusion results even if the assumption does not hold, in the sense that if something else were supposed the impossibility would result; but rather in the sense that when it is eliminated, the same impossibility results through the remaining propositions; since it is not perhaps absurd that the same false result should follow from several suppositions, eg that parallels meet, both on the assumption that the interior angle is greater than the exterior and on the assumption that a triangle contains more than two right angles.