When the flow of time is held to be not recurrent but one-way, it can be conceived of as having a beginning and perhaps an end. Some thinkers have felt that such limits can be imagined only if there is some timeless power that has set time going and intends or is set to stop it. A god who creates and then annihilates time, if he is held to be omnipotent, is often credited with having done this with a benevolent purpose that is being carried out according to plan. The omnipotent god’s plan, in this view, governs the time flow and is made manifest to humans in progressive revelations through the prophets.

This belief in Heilsgeschichte (salvational history) has been derived by Islam and Christianity from Judaism and Zoroastrianism. Late in the 12th century, the Christian seer Joachim of Fiore saw this divinely ordained spiritual progress in the time flow as unfolding in a series of three ages—those of the Father, the Son, and the Spirit. Karl Jaspers, a 20th-century Western philosopher, discerned an “axial age”—i.e., a turning point in human history—in the 6th century bce, when Confucius, the Buddha, Zarathustra, Deutero-Isaiah, and Pythagoras were supposedly alive contemporaneously. If the axial age is extended backward in time to the original Isaiah’s generation and forward to the Prophet Muhammad’s, it may perhaps be recognized as the age in which humans first sought to make direct contact with the ultimate spiritual reality behind phenomena instead of making such communication only indirectly through their nonhuman and social environments.

The belief in an omnipotent creator god, however, has been challenged. The creation of time, or of anything else, out of nothing is difficult to imagine, and, if God is not a creator but is merely a shaper, his power is limited by the intractability of the independent material with which he has had to work. Plato, in the Timaeus, conceived of God as being a nonomnipotent shaper and thus accounted for the manifest element of evil in phenomena. Marcion, a 2nd-century Christian heretic, inferred from the evil in phenomena that the creator was bad and held that a “stranger god” had come to redeem the bad creator’s work at the benevolent stranger’s cost. Zarathustra saw the phenomenal world as a battlefield between a bad god and a good one and saw time as the duration of this battle. Though he held that the good god was destined to be the victor, a god who needs to fight and win is not omnipotent. In an attenuated form, this evil adversary appears in the three Judaic religions as Satan.

Observation of historical phenomena suggests that, in spite of the manifestness of evil, there has been progress in the history of life on this planet, culminating in the emergence of humans who know themselves to be sinners yet feel themselves to be something better than inanimate matter. Charles Darwin, in his theory of the selection of mutations by the environment, sought to vindicate apparent progress in the organic realm without recourse to an extraneous god. In the history of Greek thought, the counterpart of such mutations was the swerving of atoms. After Empedocles had broken up the indivisible, motionless, and timeless reality of Parmenides and Zeno into four elements played upon alternately by Love and Strife, it was a short step for the atomists of the 5th century bce, Leucippus and Democritus, to break up reality still further into an innumerable host of minute atoms moving in time through a vacuum. Granting that one single atom had once made a single slight swerve, the build-up of observed phenomena could be accounted for on Darwinian lines. Democritus’s account of evolution survives in the fifth book of De rerum natura, written by a 1st-century-bce Roman poet, Lucretius. The credibility of both Democritus’s and Darwin’s accounts of evolution depends on the assumption that time is real and that its flow has been extraordinarily long.

Heracleitus had seen in phenomena a harmony of opposites in tension with each other and had concluded that War (i.e., Empedocles’ Strife and the Chinese yang) “is father of all and king of all.” This vision of Strife as being the dominant and creative force is grimmer than that of Strife alternating on equal terms with Love and yin and yang. In the 19th-century West, Heracleitus’s vision was revived in the view of G.W.F. Hegel, a German idealist, that progress occurs through a synthesis resulting from an encounter between a thesis and an antithesis. In political terms, Heracleitus’s vision reappeared in Karl Marx’s concept of an encounter between the bourgeoisie and the proletariat and the emergence of a classless society without a government.

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In the Zoroastrian and Jewish-Christian-Islamic vision of the time flow, time is destined to be consummated—as depicted luridly in the Revelation to John—in a terrifying climax. It has become apparent that history has been accelerating, and accumulated knowledge of the past has revealed, in retrospect, that the acceleration began about 30,000 years ago, with the transition from the Lower to the Upper Paleolithic Period, and that it has taken successive “great leaps forward” with the invention of agriculture, with the dawn of civilization, and with the progressive harnessing—within the last two centuries—of the titanic physical forces of inanimate nature. The approach of the climax foreseen intuitively by the prophets is being felt, and feared, as a coming event. Its imminence is, today, not an article of faith but a datum of observation and experience.