Listen to what Marcel is saying here. He is saying that we don’t get to pick which fanaticisms we oppose and which we embrace. He is saying that fanaticism as such must be opposed. Given that every “ism” is a fanaticism” more or less cleverly concealed, are we then to oppose all of them? Must we always be “reasonable”? Or do some things demand a level of commitment from us that cannot be described as anything less than “fanatical”? If so, then on what ground do we base our triage? How to decide which “isms” to oppose and which to champion? Everyone can agree that the fanaticisms of communism and fascism should be opposed wherever they present themselves. Many would say that capitalism (especially of the uncontrolled, freebooter variety) should equally be opposed. But what about those “isms” of which we approve? What about internationalism? Humanism? And what about that most problematical of fanaticisms, idealism? If these fanaticisms are not also to be opposed, then we need to evolve a “truth test” for good vs. bad fanaticisms, a truth test that by the nature of its structure and content would command assent from any rational moral agent. This truth test would require a lot more rigor than “Well, this fanaticism is nice to people and this fanaticism is mean.” That’s the truth test of the schoolyard, and is useless for our purposes.
This subject demands an expanded essay in itself. More: it demands a book. And who knows, maybe I might just be the one to write it. But not now, and not for awhile.