The third law comes into play when two thoughts are associated and compared. There is qualitative identity, or there is not. A is either B or not B. An animal is either a man or not a man. There is no middle class between the two to which it can be assigned. Superficial truism as this appears, we have now come upon the very battle ground of the philosophies. This is the famous “Law of the contradictories and excluded middle,” on the construction of which the whole fabric of religious dogma, and I may add of the higher metaphysics, must depend. “One of the principal retarding causes of philosophy,” remarks Professor Ferrier, “has been the want of a clear and developed doctrine of the contradictory.”[28-1] The want is as old as the days of Heraclitus of Ephesus, and lent to his subtle paradoxes that obscurity which has not yet been wholly removed. Founding his arguments on one construction of this law, expressed in the maxim, “The conceivable lies between two contradictory extremes,” Sir William Hamilton defended with his wide learning those theories of the Conditioned and the Unconditioned, the Knowable and Unknowable, which banish religion from the realm of reason and knowledge to that of faith, and cleave an impassable chasm between the human and the divine intelligence. From this unfavorable ground his orthodox followers, Mansel and Mozley, defended with ability but poor success their Christianity against Herbert Spencer and his disciples, who also accepted the same theories, but followed them out to their legitimate conclusion--a substantially atheistic one. Hamilton in this was himself but a follower of Kant, who brought this law to support his celebrated “antinomies of the human understanding,” warnings set up to all metaphysical explorers to keep off of holy ground. On another construction of it, one which sought to escape the dilemma of the contradictories by confining them to matters of the understanding, Hegel and Schelling believed they had gained the open field. They taught that in the highest domain of thought, there where it deals with questions of pure reason, the unity and limits which must be observed in matters of the understanding and which give validity to this third law, do not obtain. This view has been closely criticized, and, I think, with justice. Pretending to deal with matters of pure reason, it constantly though surreptitiously proceeds on the methods of applied logic; its conclusions are as fallacious logically as they are experimentally. The laws of thought are formal, and are as binding in transcendental subjects as in those which concern phenomena.