It is often said that the pessimism of the intellect is met with the optimism of the will. I’d like to disagree. I think pessimism is the best motivator for action, and the best condition of contemplation, for a common reason: the inevitability of illusion.
Once we escape one illusion, we inevitably enter another. Indeed, it is by creating a new illusion that we leave the old one. But to escape from illusion entirely is a hopeless fantasy, because the world is built on illusion — and so, by definition, is every world. Illusion is an incomplete picture of reality, and a given world is a small part of the whole of reality, comprising (in theory) infinitely many worlds.
So long as we are partial creatures, limited by space and time, we will remain constrained by illusion. Only God, a being one with the whole of mortal creation, is free from illusion, being prior, posterior, and present to creation as a whole. And we are not gods. We are trapped in illusion, leading to hopeless pessimism. This should not make us not act. Indeed, it should motivate us to act. If our condition is not salvageable, then it really doesn’t matter how hard we try. We will still fail. This hopelessness is our only hope — because we cannot succeed, we might as well try to do the right thing, as if we could succeed. Because there is a small chance I am wrong — and I work in order to prove myself wrong. Just in case.