On most days, I am an extreme rationalist and philosophical materialist, but I have one major weakness. Any ‘delusion’ that inspired (for example) J.S. Bach to compose the Mass In B Minor is definitely worth maintaining.
I recognize the fallacy. In Bach's culture, credo in unum deum was the only game in town. Apologists may claim that without it, the Bachs could have been a family of bakers. And perhaps their panem diem would have been divine too, but centuries later we could not partake.
At counterpoint is the old sentiment that an ordinary person must be thoroughly trained to excel, but we'd have to train a prodigy not to. Who is to say what Bach could have composed if he grasped our deep and ancient connection to all life on earth, or perceived the majesty of the cosmos as we understand it today?
Still, what a tragedy it would be not to have the Mass in B minor. Gratias agimus tibi propter magnam gloriam tuam. Dona nobis pacem.