Discussing bad ideas may seem like a departure from our subject of  Good and Evil, but some bad ideas have far ranging effects, leading to true evil. Unlike the momentary bad idea of running a stop sign, some bad ideas become embedded in religions and ideologies. Through the collective actions of many people who ascribe to those ideologies, the effects are magnified, resulting in widespread depredations, pain, suffering, and even the unnecessary loss of life.   

Evil is an objective reality that emerges from bad ideas, whether through ignorance, corrupted will, unthinking conformity, or pernicious ideologies.

The world abounds in bad ideas. To our collective good fortune most of them wither into obscurity, never rising to the level of producing evil. Many are discarded over centuries of gradual reform. A few however have survived for centuries and continue to wreak death and destruction on our species.

One of the bad ideas surviving since the 7th century CE is Sharia law and the notion that  a state and its religion should be one.  The opposite of this bad idea is seen in the success of nations that have adopted constitutional separation of church and state.  Life, Liberty, and the Pursuit of Happiness are GOOD IDEAS that focus on unalienable rights, consent of the governed, and equality, which Sharia is often criticized for undermining in its traditional or strict interpretations.

Four Historically Bad Ideas

• Religious Intolerance and Fanaticism: The notion that one’s faith is superior and must be imposed or defended through violence has sparked numerous holy wars and persecutions. Examples include the Crusades (11th-13th centuries, millions dead), the European Wars of Religion (e.g., Thirty Years’ War, 1618-1648, up to 8 million deaths), and inquisitions like the Spanish Inquisition (1478-1834, thousands executed).  These ideas persists in modern sectarian conflicts, leading to ongoing deaths.Islamic fundamentalism arose from early calls for strict scripturalism (Kharijites), developed through medieval thinkers like Ibn Taymiyya, and crystallized in modern movements such as Wahhabism, the Muslim Brotherhood, and Hamas. It draws on Qur’anic verses and Hadith emphasizing divine law, struggle (jihad), Sharia governance, often justifying armed struggle and what is currently being called terrorism.
• Nationalism and Ethnic Superiority: The belief in the supremacy of one’s nation or ethnic group, often tied to expansionism, has driven wars by dehumanizing “others.” This underpinned World War I (1914-1918, 20 million deaths) through aggressive alliances and imperial rivalries, World War II (1939-1945, 70-85 million deaths) via Nazi Aryan supremacy and Japanese imperialism, and ethnic cleansing like the Rwandan Genocide (1994, 800,000 deaths). It continues in modern ethnic conflicts.
• Imperialism and Colonial Exploitation: The ideology that stronger powers have a right to conquer and exploit weaker ones for resources or “civilizing” missions has caused centuries of wars and genocides. This includes European colonialism (e.g., Atlantic slave trade, 15th-19th centuries, 12-15 million Africans dead or enslaved; Scramble for Africa, late 19th century, millions in Congo Free State alone) and earlier empires like the Mongol conquests (13th century, 40 million deaths). It echoes in neocolonial conflicts today.
• Slavery: The institutionalized ownership and exploitation of people, often hereditary and brutal, has underpinned economies and societies for millennia, sparking slave revolts, civil wars (e.g., U.S. Civil War, 1861–1865, ~750,000 deaths), and international conflicts over abolition or trade routes. Slavery has intersected with and amplified the harms of the previous three bad ideas, often serving as a tool or justification for them. These connections are evident in historical records, where slavery reinforced divisions and motivated violence. Despite universal condemnation, slavery persists all over the world.

Numerous scholars and philosophers have argued that bad ideas, such as flawed ideologies, ignorance, self-deception, or thoughtlessness, can lead to evil outcomes, while explicitly treating evil as a real moral phenomenon rather than a lack of good. These thinkers often ground their views in historical examples of atrocities, human psychology, or ethical analysis, distinguishing evil from ordinary wrongdoing as something profoundly immoral that causes unnecessary suffering and death.

Some of the most enduring ideas are embedded as doctrine in the world’s religions.

Modern Bad Ideas

While the religious bad ideas continue, humans regularly create new bad ideas.  Many are driven by carelessness, thoughtless greed, or calculated profit motives.

The following chart illustrates a few disasters without  elaborating on who is to blame.  Nor is it possible to estimate the billions of other lifeforms directly killed or killed through loss of habitat.

Notes: Annual vs. single-event figures are not directly comparable but are ordered strictly by the numeric estimates shown. Ranges reflect variation across authoritative sources. * “Anthropogenic climate change” is a WHO projection, not observed current mortality.  NASA says, “There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.”  A Purdue University survey found that 47% of climatologists challenge the idea that humans are primarily responsible.