Now this is founded upon a confusion of ideas. No doubt death is always due to external causes. Every event in the world is determined, and wholly determined, by causes. The law of causation admits of no exception whatever. Therefore it is perfectly true that in every case of death causes precede it. But, as I explained in the last chapter, [Footnote 6] to give the cause is not to give any reason for an event. Causation is never a principle of explanation of anything. It tells us that the phenomenon A is invariably and unconditionally followed by the phenomenon B, and we call A the cause of B. But this only means that whenever B happens, it happens in a certain regular order and succession of events. But it does not tell us why B happens at all. The reason of a thing is to be {77} distinguished from its cause. The reason why a man dies is not to be found in the causes which bring about his death. The reason rather is that life has the germ of death already in it, that life is already death potentially, that Being has not-being in it. The causation of death is merely the mechanism, by the instrumentality of which, through one set of causes or another, the inevitable end is brought about. [Footnote 6: Page 64.] Not only is Being, for Heracleitus, identical with not-being, but everything in the universe has in it its own opposite. Every existent thing is a "harmony of opposite tensions." A harmony contains necessarily two opposite principles which, in spite of their opposition, reveal an underlying unity. That it is by virtue of this principle that everything in the universe exists, is the teaching of Heracleitus. All things contain their own opposites within them. In the struggle and antagonism between hostile principles consists their life, their being, their very existence. At the heart of things is conflict. If there were no conflict in a thing, it would cease to exist. This idea is expressed by Heracleitus in a variety of ways. "Strife," he says, "is the father of all things." "The one, sundering from itself, coalesces with itself, like the harmony of the bow and the lyre." "God is day and night, summer and winter, war and peace, satiety and hunger." "Join together whole and unwhole, congruous and incongruous, accordant and discordant, then comes from one all and from all one." In this sense, too, he censures Homer for having prayed that strife might cease from among gods and men. If such a prayer were granted, the universe itself would pass away. {78}