It is admitted by Mill that one _apparent_ element in this total result is the general conviction that our own existence is really distinct from the external world, and that the personal _ego_ has an essential identity distinct from the fleeting phenomena of sensation. But this persuasion is treated by him as a mere illusion--a leap beyond the original datum for which we have no authority. Of a real substance or substratum called Mind, of a real substance or substratum called Matter, underlying the series of feelings--"the thread of consciousness"--we do know and can know nothing; and in affirming the existence of such substrata we are making a supposition we can not possibly verify. The ultimate datum of speculative philosophy is not "_I think_," but simply "_Thoughts or feelings are_." The belief in a permanent subject or substance, called matter, as the ground and plexus of physical phenomena, and of a permanent subject or substance, called mind, as the ground and plexus of mental phenomena, is not a primitive and original intuition οf reason. It is simply through the action of the principle of association among the ultimate phenomena, called feelings, that this (erroneous) separation of the phenomena into two orders or aggregates--one called mind or self; the other matter, or not self--takes place; and without this curdling or associating process no such notion or belief could have been generated. "The principle of substance," as an ultimate law of thought, is, therefore, to be regarded as a transcendental dream.