So much for the sole basis of Monistic argument. When we turn to some other considerations it certainly becomes no easier to understand the claim of Monism to be scientific. In the first place, as we have seen, in order to furnish the system with any semblance of truth, it has been found necessary to attribute to the ultimate elements of matter qualities which all our experience denies them; for Professor Haeckel has told us that "the two fundamental forms of substance, ponderable matter and ether, are not dead, and only moved by extrinsic force, but they are endowed with sensation and will." Of such attributes, and that of self-mobility, it is unnecessary to add anything to what has been said already. Assuredly nothing can look less like the great ultimate reality, of whose ceaseless metamorphoses, we are but a flitting phase, than the material substances with which we can do what we like, investigating their laws, exploring their constitution, and setting them tasks which we know exactly how they will accomplish. Another point in the same connexion is no less important. What is this one _Thing_, this Ultimate and Solitary Self-existent Reality, from which Monism takes its title? Professor Haeckel has told us of two fundamental forms of substance,--ponderable matter and ether. These he evidently supposes, as his creed requires, to be radically the same: but what right has he to take such a supposition for a fact? and unless this unity be a fact, what becomes of Monism? What has Science ever discovered that can justify any one in speaking of Ether and Matter as one and the same? How, then, can a theory that assumes their identity be termed "scientific?"