1. What can I know?
2. What should I do?
3. What may I hope?
The three questions  correspond to the three "theological virtues" of faith, hope, and charity.  Faith in God's word is the Christian answer to "What can I know?" Love of God and neighbor is the Christian answer to "What should I do?" And hope for Gods' Kingdom, the Kingdom of heaven, is the Christian answer to "What may I hope?" Just as faith fulfills the mind's deepest quest for truth and as love fulfills the moral will's deepest quest for goodness, so the hope of heaven fulfills the heart's deepest quest for joy.
It is the quest that moves irrepressibly through the world's great myths and religions, the masterpieces of its greatest artists and writers, and the dreams that rise from the primordial depths of our unconscious. However different the heavens hoped for, wherever there is humanity, there is hope.
The question of hope is at least as ultimate as the other two great questions. For it means "what is the point and purpose of life? Why was I born? Why am I living? What's it all about, Alfie?"
Most people in our modern Western society do not have any clear or solid answer to this question. Most of us live without knowing what we live for. Surely this is life's greatest tragedy, far worse than death. Living for no reason is not living, but mere existing, mere surviving. As Viktor Frankl found in a Nazi concentration camp, our deepest, rock-bottom need is not pleasure, as Freud thought, or power, as Adler thought, but meaning and purpose, "a reason to live and a reason to die".  We need a meaning to life more than we need life itself.
Millions all around us are living the tragedy of meaningless life, the "life" of spiritual death. That is what makes our society more radically different from every society in history: not that it can fly to the moon, enfranchise more voters, have the grossest national product, conquer disease, or even blow up the entire planet, but that is does not know why it exists.
Every past society gave its members answers to all three great questions. It transmitted the teachings of its sages, saints, mystics, gurus, philosophers, or gods through tradition. For the first time in history, society no longer regards tradition as sacred; in fact, it no longer regards it at all. We are the first tree that has uprooted itself from the universal soil. If we are to find an answer to the question "For what may I hope?" we must find the answer individually; our society simply does not know. The only sound we hear from our noisy society concerning the most important questions in the world is the sound of silence.
How has this silence come about? How is it that the society that "knows it all" about everything knows nothing about Everything? How has the knowledge explosion exploded away the supreme knowledge? Why have we thrown away the road map just as we've souped up the engine? We must retrace the steps by which we have come to this dead end; to recapture hope we must diagnose the causes of our hopelessness before we begin to prescribe a remedy. Before we undertake the main task of this book, the exploration of the deepest hope of the human heart, the hope for heaven, we must first answer two preliminary questions: first, why our society is so silent, and second, how our hearts can substitute for our society in being our teachers and guides on our quest for hope, our quest for heaven.
The History of Hope
From earliest times, humanity has hoped for heaven. The earliest artifacts are burial mounds. The dead were always prepared for the great journey. However various the forms, belief in an afterlife is coterminous with humanity.
The Hebrew conception of heaven arises in exactly the opposite way from the pagan one; instead of rising out of humanity's heart, it descends from God's. From the beginning of the story, God tells humanity what he wants instead of humanity telling God what it wants. Instead of humanity making the gods in its image, God makes humanity in His image; and instead of earth making heaven in its image, heaven makes earth in its image. Thus the greatest Jew teaches us to pray: "Thy kingdom come ... on earth as it is in heaven."
The Jews are "the chosen people"--through no merit of their own, God insists--chosen to be the messengers of hope for the world, the world's collective prophet, God's mouthpiece. God teaches them, and through them the world, three things: who he is, what they must do, and for what they may hope. For the third, he promises many things, some obscure, some incredible, as when he says he will raise the dead.  God says he will show them something (whether on this earth or not is obscure) that "eye has not seen, ear has not heard, nor has it entered into the heart of man." 
The good Jew therefore does not speculate about heaven. If it has not entered into "the heart of man," well then, whatever has entered into "the heart of man" is not it. Let God define it and provide it, not humanity. Only when God speaks do we know with certainty, and when God speaks obscurely, we know only obscurely. Jews, unlike Christians, do not believe God has spoken clearly about the afterlife (at least not yet), and they will not run ahead of God--a proper and admirable restraint when contrasted with the extravagant myths of the rest of the world, who succumb to the irresistible temptation to fill in with human imagination the gaps left in God's revelation.
The Greeks are the other root of the tree of Western civilization. The Jews gave us conscience; the Greeks, reason. The Jews gave us the laws of morality, of what ought to be; the Greeks gave us the laws of thought and of being of what is. And their philosophers discovered a new concept of God and a new concept of heaven. While the priests were repeating their stories of fickle and fallible gods with their Olympian shenanigans and imaginative afterworlds, underworlds, or overworlds, the philosophers substituted impersonal but perfect essences for the personal but imperfect gods and a heaven of absolute Truth and Goodness for one of pleasures or pains. Not Zeus, but Justice, not Aphrodite, but Beauty, not Apollo, but Truth were the true gods: perfect unpersons rather than imperfect persons. (The Jews, meanwhile, were worshipping the Perfect Person, transcending the Greek alternatives.) The heaven corresponding to the Greek philosophers' theology was a timeless, spaceless realm of pure spirit, pure mind, pure knowledge of eternal essences instead of the priests' gloomy underworlds of Tartarus and Hades, earthly otherworlds of Elysian Fields, or astronomical overworlds of heroes turned into constellations.
Two of these heavenly essences stand out as ultimate values: Truth and Goodness. Even the gods are judged by these values and found wanting; that is why Socrates was executed, for "not believing in the gods of the State".  Plato asks, "is a holy thing holy because the gods approve it, or do the gods approve it because it is holy?"  The priests say the former; the philosophers, the latter. For them the two eternal essences, Goodness and Truth, stand above the Greek gods. But they do not stand above the Jewish God, the God who is Goodness and Truth, emeth, fidelity, trustworthiness. The Greeks discovered two divine attributes; the Jews were discovered by the God who has them.
Hebraism and Hellenism meet--Hebraism in its Christianized form, Hellenism in its Romanized form. But these forms remain Hebraic and Hellenic in substance. Christ was not an alien import; he did not ask Jews to convert to a new religion but claimed to be their prophets' Messiah. And Rome remained a Greek mind in a Roman body. The Empire added emperors aplenty, the material accoutrements of roads, armies, and political power, but not one important new philosophy.
The meeting and blending of these two great rivers, the biblical (Judeo-Christian) and the classical (Greco-Roman) produced the Middle Ages. Medieval thinkers were intensely conscious of being inheritors and synthesizers, preservers and blenders of two ancient foods. As medieval theology synthesized the personality of YHWH (incarnated in Christ) with the timeless perfection of the philosophers' essences, the medieval picture of heaven synthesized the biblical imagery of love and joyful worship of God with the Greek philosophical heaven of the contemplation of eternal Truth.
But the Middle Ages are no longer. The Renaissance and the Reformation disintegrated the medieval synthesis, divorced the couple that had been stormily but creatively married. These two sources of modernity both harked back to pre-medieval ideals: the Renaissance longed to return to Greco-Roman humanism and rationalism, and the Reformation longed to return to a simple biblical faith.
From the Reformation emerged a Protestantism whose essential vision of human destiny was in agreement with medieval Catholicism, since both were rooted in biblical revelation. But from the Renaissance emerged something radically new in human history: a secular society with a secular summum bonum. Of the twenty-one civilizations Toynbee distinguishes in his monumental Study of History, the first twenty kept some sort of religious basis and purpose; ours is history's most unique experiment. It remains to be seen how long a civilization can survive without the use of spiritual energy, without a supernatural source of life.
What purpose is substituted for the service of God and the hope of heaven? The conquest of nature, first by the ineffective attempt of magic, then by the reliable way of technology. But the difference between these two means is minor compared to the difference between their common new end and the common old end: "There is something which unites magic and applied science while separating both from the 'wisdom' of earlier ages. For the wise men of old the cardinal problem had been how to conform the soul to reality, and the solution had been knowledge, self-discipline, and virtue. For magic and applied science alike, the problem is how to subdue reality to the wishes of men: the solution is a technique."
This new purpose in life is logically connected with a new vision of the nature of reality, for one's life view and world view (Lebenschauung and Weltanschauung) hang together. As long as the nature of ultimate reality was thought to be trans-human--some sort of God or gods--our fundamental relation to reality was to conform, not to conquer. But once the gods drop out of view and "reality" comes to mean merely material nature--the subhuman, not the superhuman--our life's business is not to conform to it but to conquer it for our own purposes. Bacon trumpets the new age with slogans like "knowledge for power" and "Man's conquest of Nature." These replace the "impractical" and "passive" traditional goals of knowledge for truth and of being conquered by God.
Think of humanity as a tube with two openings. The openings can be either open or closed, as we choose. Think of God, or superhuman reality, as above the tube, and nature, or subhuman reality, as below it. Traditional religious wisdom tells us to be open at both ends so God can flow in one end and out the other: in the receptive end first by faith and then out the active end by works. But if the top opening is closed, our business becomes exclusively human action in the world, without a plug-in to divine power. This is technologism, "Man's conquest of Nature."
There is a third possibility: the tube could be closed at the bottom and open at the top. This would characterize Hinduism and Buddhism, for which the world is illusion (maya) or temptation, and the sole end of life is the realization of oneness with trans-human ultimate reality. Oriental mysticism minimizes worldly action; modern Western secularism denies receptivity to God; and the classical Western tradition synthesizes the two, giving priority to the God-relationship, for we must first be directed by God before we can wisely direct our world.
Once modernity denies or ignores God, there are only two realities left: humanity and nature. If God is not our end and hope, we must find that hope in ourselves or in nature. Thus emerge modernity's two new kingdoms, the Kingdom of Self and the Kingdom of This World: the twin towers of Babel II. Judging by the outcome of Babel I, the prognosis does not look good.
The Two Modern Idol-Kingdoms
An idol is anything that is not God but is treated as God: any creature set up as our final end, hope, meaning, and joy. Anything--anything--can be an idol. Religion can be an idol. Religion is not God but the worship of God; idolizing religion means worshipping worship. That's like being in love with love rather than with a person. Love too can be an idol, for "God is love" but love is not God. Every divine attribute, separated from the divine person, becomes an idol. God is Truth, but Truth is not God. God is just, but Justice is not God. The first commandment is surely the one most frequently broken, and the apostle John does well to end his first letter with the warning, "Little children, keep yourselves from idols." 
Since an idol is not God, no matter how sincerely or passionately it is treated as God, it is bound to break the heart of its worshipper, sooner or later. Good motives for idolatry cannot remove the objective fact that the idol is an unreality. "Food in dreams is exactly like real food, yet what we eat in our dreams does not nourish: for we are dreaming."  You can't get blood from a stone or divine joy from nondivine things.
There are two idols, two false kingdoms, in the modern world rather than just one because the modern world is a split world, an alienated world, a world of dualism. Humanity and nature, siblings from a common Father, became alienated from each other when humanity, nature's priest and steward, became alienated from God. In the Genesis story thorns and thistles appear after Adam's Fall, and pain in childbirth for Eve. 
The alienation between humanity and nature begun at the Fall is exacerbated by Renaissance humanism, and its two forms herald the two modern idol-kingdoms. First, the southern European Renaissance places humanity in the foreground and God in the background; then the northern European Renaissance puts nature in the foreground and the road to utopia becomes the conquest of nature.
Descartes, the father of modern philosophy and child of both Renaissances, separates humanity and nature more sharply than ever before. Humanity's essence is merely mind and nature's is merely matter; and mind and matter are two clear and distinct ideas. For mind does not occupy space, but matter does; and matter does not have any consciousness, but mind does. The fact that we find the mind-matter distinction clear and self-evident is a measure of how influential Cartesian dualism is.
But the alienation is not merely between ourselves and nature but also within ourselves between mind and body. Descartes sees the human being as a "ghost in a machine," a pure spirit or mind in a purely material body, and we have no idea how a ghostly finger can push the buttons of a bodily machine.  We do not recognize ourselves in this picture of the ghost in the machine; yet it is the picture to which modern common sense naturally gravitates. We know we are not ghosts in machines, but we do not know what we are. We know reality cannot be two totally different and unconnected things, but we do not know what reality ultimately is--that is, if "we" are typically modern.
The overcoming of dualism is monism--but a monism of what? Matter or spirit? Both solutions have emerged in modern philosophy. LaMettrie and Hobbes are early modern materialists; Spinoza and Leibnitz are early modern spiritualists. Materialism reduces spirit to matter; spiritualism reduces matter to spirit. Later, with Kant, spiritualism changes from an objective to a subjective spiritualism. Ever since Kant, the modern dualism has been not merely between matter and spirit but between objective matter and subjective spirit. The two idol-kingdoms are built in these two realms: the Kingdom of This World in the realm of objective matter at the expense of spirit and the Kingdom of the Self in the realm of subjective spirit at the expense of the objective. Subjective truth replaces objective truth; subjective values replace objective values. Both kingdoms are alternatives to the Kingdom of God, which is built in the realm of objective spirit. God is objective spirit, and when "God is dead," the objective world is reduced to matter and the spiritual world is reduced to subjectivity. That is our dualism.
To overcome this dualism and to relieve the anxiety its alienation causes, we take refuge in one or the other of the two monisms. We dare not see both halves of our split personality at once. Buber writes memorably about this in an image:
At times the man, shuddering at the alienation between the I and the world, comes to reflect that something is to be done. ... And thought, ready with its service and its art, paints with its well-known speed one--no, two rows of pictures, on the right wall and on the left. On the one there is ... the universe. ... On the other wall there takes place the soul .... Thenceforth, if ever the man shudders at the alienation, and the world strikes terror in his heart, he looks up (to right or left, just as it may chance) and sees a picture. There he sees that the I is embedded in the world and there is really no I at all--so the world can do nothing to the I, and he is put at ease; or he sees that the world is embedded in the I, and that there is really no world at all--so the world can do nothing to the I, and he is put at ease.
But a moment comes, and it is near, when the shuddering man looks up and sees both pictures in a flash together. And a deeper shudder seizes him. 
The only overcoming of that deeper shudder of alienation is in the common Father of I and world. Thus Buber's next line is, "the extended lines of relations meet in the eternal Thou."
 Emmanuel Kant, Critique of Pure Reason, trans. Norman Kemp Smith (New York: Macmillan, 1958), p. 635: "All the interests of my reason, speculative as well as practical, combine in the three following questions: (1) What can I know? (2) What ought I to do? (3) What may I hope?"
 Aquinas. Summa Theologiae I-II. 62, 3.
 Viktor E. Frankl, Man's Search for Meaning (New York; Washington Square Press, 1963). Cf. John Powell, A Reason to Live, A Reason to Die (Niles, Ill.: Argus Communications, 1972).
 Matt. 6:10. Scriptural quotations are from the Revised Standard Version unless otherwise noted.
 Deut. 7:6-8.
 Isa. 25:8; Ezek. 37:12-14; Job 19:25-27.
 1 Cor. 2:9 cf. Isa. 64:4, 65:17.
 Plato, Apology of Socrates 24b.
 Plato, Euthyphro 10a.
 C. S. Lewis, The Abolition of Man (New York: Macmillan, (1965), pp. 87-88.
 Francis Bacon, Magna Instauratio, Preface; Novum Organum 2. 20.
 1 John 5:21.
 Augustine, Confessions 3. 6.
 Gen. 3:16-19.
 The phrase is from Gilbert Ryle. The Concept of Mind (New York: Barnes & Noble, 1949).
 Martin Buber, I And Thou, trans. Ronald Gregor Smith (New York: Charles Scribner's Sons, 1958), pp. 70-72.
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Peter Kreeft, Ph.D., is a professor of philosophy at Boston College. He is an alumnus of Calvin College (AB 1959) and Fordham University (MA 1961, Ph.D., 1965). He taught at Villanova University from 1962-1965, and has been at Boston College since 1965.
He is the author of numerous books (over forty and counting) including: C.S. Lewis for the Third Millennium, Fundamentals of the Faith, Catholic Christianity, Back to Virtue, and Three Approaches to Abortion. More info about Kreeft and his many Ignatius Press books can be found on his IgnatiusInsight.com author page.