This could possibly be the rallying cry of postmodernism. If postmodernism had a rallying cry.
A brief history lesson
Rational thought is born on the shores of the Mediterranean Sea, with old, wisened men with long white beards discussing piety and immortality under the watchful tutelage of the elenchus. The memory of Ancient Greece will last as long as its writings are translated into the crude vernacular of the present day. It becomes necessary, from time to time, to remind the world that there was once a country with such beauty, grace, and courage that the mundane world, in which we now live, allowed to slip away. The arabians kept the old ways bottled for centuries and, for a time, embraced the falsafah.
The Enlightenment was the climax of rational thought. Issac Newton had circumscribed the heavens with the blessing of the Newtonian Method, and thus started a new faith in the power of logic. The Deist movement was hard-pressed to explain theodicy, and yet they gave rise to the idea of God as an engineer. People began applying the Newtonian method to everything -- philosophy (George Berkeley, David Hume, John Locke...); art (Rococo, Neo-Classical, Baroque); the social sciences... and even things we couldn't properly call science today.
Fast-forward through to the birth of Romanticism. Cameras were better at realism than any painter could ever be, so the artists abandoned reality and became caught up in their dreams. Impressionism. Expressionism. Drugs. Sex. Lots of sex. Yet somehow, philosophes kept the faith. Jean Jaurès and others fight the beginning of World War, stemming the tide with the power of socialism and unreasonably charismatic speeches. They weren't the only ones who believed they were right -- the Enlightenment made the wise so caught up in their own hubris that they couldn't believe they could be wrong.
Jaurès dies. World War I breaks out as nationalism fed by honor and pride sends millions to early graves. Millions. Reason leads the world to the brink of self-annihilation.
Then twenty years pass, and we do it all over again.
And that brings us up to 1950. Japan and Germany recover from their defeat, but two powers -- one Communist, the other Capitalist -- build up a stockpile of insanely powerful nuclear weapons and settle in for a winter of uneasy peace.
Doesn't that sound convincing?
Mathematics: David Hilbert's dream for mathematics fails. Gödel sticks in one dagger, Turing stabs the second. Now mathematicians continue on, ignoring the problem of consistency as long as it doesn't directly affect their work.
Physics: Albert Einstein does his thing, and gives the definitive counter-example to the earlier notion of one nature under Newton. Modern Physics pops up some very weird, counter-intuitive ideas about how the world should work. Now physicists continue using old methods where they work, and don't give up the Newtonian method.
Philosophy: Oh, the philosophers try to hold on to rational thought. Frederick Nietzsche kills God. God kills Nietzsche. A new wave of nihilist-reactionary philosophy and religion come into existence. Objectivism, Scientology, Unitarianism: all are reactions against the uncertainty of the postmodern world. Many are seen as cults, and are ignored. And still, no one understands Immanuel Kant.
Politics: Even with Marx dead, socialism sneaks in and begins to wear away at capitalism. The Soviet Union falls, and we finally learn what a farce the past twenty years have been. They had one-tenth the military might of the United States. All that time we spent forgetting that America had dropped two weapons of mass destruction and was now on the 'right path' (We'll never do it again. Promise.) comes to bear as they become the strongest power in the world. They shove democracy and freedom down the world's throat, insisting it is the proper way.
Conclusion
These past thirty years were the second Enlightenment and Romantic Era, and we missed the boat. All your radical, post-modern ideas have already occured to others, and were thrown out like last year's garbage. The science of the 70's, 80's, and 90's was still newton in implementation, and the philosophy that backed them still depends on the certainty of logic.
Is rational thought doomed? No. Man does a fine job dooming himself with pride, ignorance, and his overwhelming need follow the one true path. We are posed at a fork in the road with a million branches, all streaming with garish golden light. Yet all of them circle back to where we started. There we will stand, looking hopelessly and the glory and splendor of the appearance of Truth, in petty ignorance to the ghost of an ancient man with one hand pointed to the heavens, and the other pointed towards a dusty, barren path in the sand.
This is by no means a complete, nor rigorous, treatment of the subject at hand. 300 years of history cannot be compressed into a single node, no matter how long. When someone tells you that rational thought is doomed, yet in many of the cases we see a constant conjunction between reason and pride, one wonders if we can really blame rational thought.