Ideas are such intangible things that it is hard to believe that they have had a huge impact on the lives of people who are not intellectuals and who, in many cases, have paid little attention to those ideas. Yet both secular and religious ideas have moved the emotions of many-- and have moved leaders who moved armies.
When we look back on the Spanish Inquisition, on the Crusades of the past and the Jihads of the past and present, we see chilling examples of the effects of ideas. But the secular ideologies of the 20th century killed millions more people in Germany, Russia and China-- and similarly in pursuit of higher goals, even if those ideals were used cynically by those with power, as in the past.
If there is any lesson in the history of ideas, it is that good intentions tell you nothing about the actual consequences. But intellectuals who generate ideas do not have to pay the consequences.
Academic intellectuals are shielded by the principles of academic freedom and journalists in democratic societies are shielded by the principle of freedom of the press. Seldom do those who produce or peddle dangerous, or even fatal, ideas have to pay a price, even in a loss of credibility.
Who blames Rachel Carson, an environmentalist icon, because her crusading writings against DDT led to the ban of this insecticide in countries around the world-- followed by a resurgence of malaria that killed, and continues to kill, millions of people in tropical Third World countries?
Even political leaders have been judged by how noble their ideas sounded, rather than by how disastrous their consequences were. Woodrow Wilson-- our only president with a Ph.D.-- was an academic intellectual for years before entering politics, and his ideas about a war to end wars, making the world safe for democracy, and the right of self-determination of peoples, have been revered in utter disregard of what happened when Wilson's notions were put into practice in the real world.
No one today takes seriously the idea that the First World War was a war to end wars, and many now see it as setting the stage for a Second World War. Indeed there were those who predicted this result at the time. But they were not listened to, much less lionized, like Woodrow Wilson.