Thus, like Xenophanes, Parmenides draws a deep division between the world of reason and the world of sensation, between probative argument and the guess-work of sense-impressions. The former is the world of Being, the world of that which truly is, self-existent, uncreated, unending, unmoved, unchanging, ever self-poised and self-sufficient, like a sphere. [98] Knowledge is of this, and of this only, and as such, knowledge is identical with its object; for outside this known reality there is nothing. In other words, Knowledge can only be of that which is, and that which is alone can know. All things which mortals have imagined to be realities are but words; as of the birth and death of things, of things which were and have ceased to be, of here and there, of now and then. It is obvious enough that in all this, and in much more to the same effect reiterated throughout the poem, we have no more than a statement, in various forms of negation, of the inconceivability by human reason of that passage from _being_ as such, to that world of phenomena which is now, but was not before, {36} and will cease to be,--from _being_ to _becoming_, from eternity to time, from the infinite to the finite (or, as Parmenides preferred to call it, from the perfect to the imperfect, the definite to the indefinite). In all this Parmenides was not contradicting such observed facts as generation, or motion, or life, or death; he was talking of a world which has nothing to do with observation; he was endeavouring to grasp what was assumed or necessarily implied as a prior condition of observation, or of a world to observe.