From Manichaean dualism and Augustine's privation to Leibniz's best of all worlds, Dostoevsky's rebellion, and Arendt's banality — the problem that will not resolve.
What is evil — a positive force, a mere absence of good, or a human capacity we would rather not name?
Evil is the wound at the centre of every theology and much of philosophy. If a good and all-powerful God exists, why is there so much suffering and cruelty? The Manichees answered with two eternal powers of light and darkness; Augustine replied that evil is no thing at all but a privation, a hole in the good, chosen by a will turned from God. Leibniz tried to prove this the best of all possible worlds and coined 'theodicy'; Hume and later Dostoevsky's Ivan Karamazov threw the child's tear back in its face. Kant found a 'radical evil' rooted in the human heart, and after the death camps Arendt spoke of evil's disturbing 'banality' in ordinary functionaries. Whether evil is metaphysical, moral, or merely natural, thinking about it forces every other concept — God, freedom, justice — to declare itself.
Manichaeism (dualism)
Reality is the battleground of two eternal, co-original principles: a kingdom of Light and spirit and a kingdom of Darkness and matter. Evil is not a lack but a positive substance, an invading power in which our bodies and the material world are entangled. Salvation is the liberation of the imprisoned particles of light from the dark matter that holds them.
Manichaean scriptures (largely reconstructed); reported by Augustine.
Neoplatonism
Evil has no independent existence; it is the utter privation of good, the darkness at the lowest limit of emanation where reality fades toward non-being. Matter, as the last and faintest overflow from the One, is the 'primary evil' precisely because it lacks form and measure. Moral evil in the soul is a turning of attention away from the intelligible toward this formless deficiency.
The Enneads, I.8 ('On What Are and Whence Come Evils').
Christian (Patristic)
Against the Manichees, evil is not a substance but a privation of good (privatio boni), a corruption or absence in something that is itself good insofar as it exists. Moral evil arises from the free will's disordered love — choosing lesser goods over God — as in the famous theft of pears he wanted only for the sin's sake. God permits evil only because he can bring greater good out of it.
Confessions; Enchiridion; The City of God.
Scholasticism
Evil is the privation of a good that ought to be present, and it has no efficient cause of its own but only a 'deficient' one. He distinguishes the evil of fault (moral sin) from the evil of penalty (suffering), both parasitic on good. God wills the order of the whole, in which the corruption of one thing serves the good of another, and permits moral evil without being its author.
Summa Theologiae, I, qq. 48–49; On Evil (De Malo).
Rationalism
God, being perfect, created the best of all possible worlds; the evil it contains is the price of a whole richer in good than any alternative. He distinguishes metaphysical evil (finitude), physical evil (suffering), and moral evil (sin), the first being the root of the rest. Coining the term 'theodicy', he argues that a world with free creatures and its harmonies could not exist without permitting these imperfections.
Theodicy (1710).
Empiricism / skepticism
The sheer quantity of suffering in nature makes the traditional inference to a benevolent, omnipotent deity unwarranted. Restating Epicurus' old dilemma — is God willing but unable, or able but unwilling? — he argues the world's mixed character fits an indifferent cause better than a perfectly good one. At best the evidence leaves the moral attributes of any first cause wholly undetermined.
Dialogues Concerning Natural Religion (1779), Parts X–XI.
German idealism / critical philosophy
There is a 'radical evil' in human nature: a propensity to subordinate the moral law to self-love, to make exceptions in our own favour. This is not mere weakness or animal instinct but a freely adopted corruption of the will's ordering of its incentives. Because it is freely chosen, evil can in principle be overcome by a moral 'revolution' of the disposition, though the propensity is universal.
Religion within the Boundaries of Mere Reason (1793), Book I.
Post-Kantian pessimism
The world is the objectification of a blind, insatiable Will, and existence is therefore shot through with suffering, striving without rest. Evil and cruelty spring from the Will's self-division, each individual asserting itself at others' expense; malice is the will affirming itself by others' pain. Release comes only through compassion, which sees through the illusion of separateness, and finally through the denial of the will to live.
The World as Will and Representation (1818/1844).
Russian literature / Christian existentialism
Through Ivan Karamazov he poses the sharpest form of the problem: no future harmony can justify the torture of a single innocent child, so he 'returns the ticket' to God's world. Evil is dramatized as the seductive logic of 'if God does not exist, everything is permitted', tested to destruction in his characters. His answer is not an argument but the active, humble love embodied in Alyosha and the elder Zosima.
The Brothers Karamazov (1880), 'Rebellion' and 'The Grand Inquisitor'.
Genealogical critique
'Evil' is a category invented by ressentiment: the weak reinterpreted the strength and vitality of their masters as wickedness, inverting the noble 'good/bad' into the moral 'good/evil'. What Christianity brands evil — pride, assertion, the will to power — is often the very energy of life. To move 'beyond good and evil' is not to endorse cruelty but to question the value and origin of the moral opposition itself.
Beyond Good and Evil (1886); On the Genealogy of Morality (1887).
Christian mysticism / Platonism
The extreme form of evil is 'affliction' (malheur), a suffering that crushes the soul and marks it with the impersonal violence of force. Imaginary evil is romantic and varied while real evil is 'gloomy, monotonous, barren, boring'; the reverse is true of good. Only by consenting to the void, without seeking false consolation, can the soul remain turned toward God and let grace, not violence, enter.
Gravity and Grace; The Need for Roots.
Political theory
Reporting on Eichmann's trial, she coined 'the banality of evil': monstrous crimes can be committed not by demonic monsters but by unthinking functionaries incapable of judging from another's standpoint. Evil on this scale is 'thought-defying', lacking depth or radical roots, spreading like a fungus over the surface of the world. The remedy she looks to is the faculty of thinking and judging that resists mere conformity.
Eichmann in Jerusalem: A Report on the Banality of Evil (1963).
Contemporary moral philosophy
The problem of evil, not epistemology, is the guiding thread of modern philosophy, running from the Lisbon earthquake to Auschwitz. She distinguishes two lineages: one from Rousseau that seeks to make evil intelligible, another from Voltaire and the Marquis de Sade that insists it remains an affront to reason. Evil marks the gap between the world as it is and as it ought to be, a gap thinking must keep open rather than explain away.
Evil in Modern Thought (2002).