These same Bauddhas discuss the highest end of man from four standpoints. Celebrated under the designations of Mádhyamika, Yogáchára, Sautrántika, and Vaibháshika, these Buddhists adopt respectively the doctrines of a universal void (nihilism), an external void (subjective idealism), the inferribility of external objects (representationism), and the perceptibility of external objects (presentationism).[31] Though the venerated Buddha be the only one teacher (his disciples) are fourfold in consequence of this diversity of views; just as when one has said, "The sun has set," the adulterer, the thief, the divinity student, and others understand that it is time to set about their assignations, their theft, their religious duties, and so forth, according to their several inclinations. It is to be borne in mind that four points of view have been laid out, viz., (1.) All is momentary, momentary; (2.) all is pain, pain; (3.) all is like itself alone; (4.) all is void, void. Of these points of view, the momentariness of fleeting things, blue and so forth (_i.e._, whatever be their quality), is to be inferred from their existence; thus, whatever _is_ is momentary (or fluxional) like a bank of clouds, and all these things _are_.[32] Nor may any one object that the middle term (existence) is unestablished; for an existence consisting of practical efficiency is established by perception to belong to the blue and other momentary things; and the exclusion of existence from that which is not momentary is established, provided that we exclude from it the non-momentary succession and simultaneity, according to the rule that exclusion of the continent is exclusion of the contained. Now this practical efficiency (here identified with existence) is contained under succession and simultaneity, and no medium is possible between succession and non-succession (or simultaneity); there being a manifest absurdity in thinking otherwise, according to the rule-- "In a reciprocal contradiction there exists no ulterior alternative; "Nor is their unity in contradictories, there being a repugnance in the very statement."[33] And this succession and simultaneity being excluded from the permanent, and also excluding from the permanent all practical efficiency, determine existence of the alternative of momentariness.--Q.E.D.