Philosophy of war

The philosophy of war is the area of philosophy devoted to examining issues such as the causes of war, the relationship between war and human nature, and the ethics of war. Certain aspects of the philosophy of war overlap with the philosophy of history, political philosophy, international relations and the philosophy of law.

Perhaps the greatest and most influential work in the philosophy of war is Carl von Clausewitz's On War, published in 1832. It combines observations on strategy with questions about human nature and the purpose of war. Clausewitz especially examines the teleology of war: whether war is a means to an end outside itself or whether it can be an end in itself. He concludes that the latter cannot be so, and that war is "politics by different means"; i.e. that war must not exist only for its own sake. It must serve some purpose for the state.

Leo Tolstoy's 1869 novel War and Peace contains frequent philosophical digressions on the philosophy of war (and broader metaphysical speculations derived from Christianity and from Tolstoy's observations of the Napoleonic Wars). It was influential on later thought about war. Tolstoy's Christian-centered philosophy of war (especially his essays "A Letter to a Hindu" (1908) and "The Kingdom of God is Within You" (1894)) directly influenced Gandhi's Hinduism-centered non-violent resistance philosophy.

Writing in 1869, Genrikh Leer [ru] emphasized the favorable effects of war on nations: "[...] war emerges as a powerful tool in the matter of improving the internal, moral and material life of peoples [...]."

While Sun Tzu's The Art of War (5th century BCE), focuses mostly on weaponry and strategy instead of on philosophy, various commentators have broadened his observations into philosophies applied in situations extending well beyond war itself such as competition or management (see the main Wikipedia article on The Art of War for a discussion of the application of Sun Tzu's philosophy to areas other than war). In the early 16th century, parts of Niccolò Machiavelli's masterpiece The Prince (as well as his Discourses) and parts of Machiavelli's own work titled The Art of War discuss some philosophical points relating to war, though neither book could be said to be a work in the philosophy of war.

The Indian Hindu epic, the Mahabharata, offers the first written discussions of a "just war" (dharma-yuddha or "righteous war"). In it, one of five ruling brothers (Pandavas) asks if the suffering caused by war can ever be justified. A long discussion then ensues between the siblings, establishing criteria like proportionality (chariots cannot attack cavalry, only other chariots; no attacking people in distress), just means (no poisoned or barbed arrows), just cause (no attacking out of rage), and fair treatment of captives and the wounded. The philosophy of just war theorizes what aspects of war are justifiable according to morally acceptable principles. Just war theory is based upon four core criteria to be followed by those determined to go to war. The four principles are as follows: just authority; just cause; right intention; last resort.

The criterion of just authority refers to the determined legality of going to war, and whether the concept of war and the pursuit of it has been legally processed and justified.

Just cause is a justifiable reason that war is the appropriate and necessary response. If war can be avoided, that must be determined first, according to the philosophy of just war theory.