War is an occurrence of intense and prolonged violence between nations and states. It occurs over political power, territorial and ethnic issues, societal stresses such as poverty and injustice, or the supply of weapons and ammunition. It also takes the lives of civilians. Many people consider themselves to be pacifists, but others recognize the necessity of military action to support or defend the security and safety of individuals, communities and nations from attack. They are still concerned about the moral dimensions of war, however: what is and is not permissible, or justifiable, as targets for warfare; what strategies and tactics are fair game; and whether treaties and covenants should be negotiated to reduce the risk of future conflict.

Philosophers have debated the causes of war for centuries. Some, such as Cicero and Hugo Grotius, define it as a “contention by force,” while Denis Diderot writes that it is a “convulsive and violent disease of the body politic.” Karl von Clausewitz argues that war is “the continuation of politics by other means.”

A more sophisticated approach is to examine the conditions for war to prevent it from occurring. Some philosophers look at the factors that must exist for the threat of violence to be averted: bumbling rulers; hatreds, prejudices and misunderstandings; access to weapons; economic limitations and scarcity of resources; the tendency toward “reciprocal” and “escalating” retaliation; and so on. Some scholars argue that these are not the chief reasons for war, however.

Other philosophers consider the intangible and ideological incentives that motivate leaders to fight: God’s glory, nationalist ideals, or other visionary goals. Think, for example, of Vladimir Putin’s obsession with the Soviet Union’s glory and his refusal to compromise on Ukraine; or liberation movements in colonial areas that were willing to suffer the ruin and risks of war partly in pursuit of an ideal.

The consequences of war go well beyond the immediate physical damage and loss of life. Repeated exposure to traumatic events can cause mental and emotional distress, such as post-traumatic stress disorder (PTSD), and lead to substance abuse, depression and other health problems. Moreover, it is difficult to sustain stable economies in war zones and many citizens lose their jobs and homes as a result of conflict. Consequently, they are less likely to be able to afford healthy foods and other essential goods. This leads to malnutrition, weakened immune systems and longer-term health issues such as heart disease. This can in turn contribute to a vicious cycle of increased conflict, greater poverty and even more violence. Ultimately, the only way to avoid this is to prevent conflict before it begins. This is why it is important to promote peace education, work for a global arms treaty and reduce the proliferation of weapons in developing countries, which bear the brunt of death and destruction from armed conflict.