From Pope Benedict:
“Above all, however, we must confirm that this Enlightenment philosophy, with its related culture, is incomplete. It conspicuously cuts off its own historical roots, depriving itself of the powerful sources from which it sprang. It detaches itself from what we might call the basic memory of mankind, without which reason loses its orientation, for now the guiding principle is that man’s capability determines what he does. If you know how to do something, then you are also permitted to do it; to know how to do something, but not be able to do it, is a state of affairs that no longer exists, since it would run counter to liberty– which is the absolute, supreme value. But man knows how to do many things, and this knowledge increases all the time. If this knowledge does not find its criterion in a moral norm, it becomes a power for destruction, as we cal already see in the world around us. Man knows how to clone human beings, and therefore he does so. Man knows how to use human beings as “storerooms” of organs for other men, and therefore he does so. He does so, because this seems somehow demanded by his own liberty. Man knows how to build atomic bombs, and therefore he makes them, and is willing in principle to use them, too. Even terrorism is ultimately based on this modality of man’s “self-authorization”, not on the teachings of the Qu’ran. The radical detachment of Enlightenment philosophy from its roots ultimately leads it to dispense with man. The spokesmen of the natural sciences tell us that man basically does not possess any liberty– in total contradiction of the starting point of the whole question. The more advanced spokesmen of a philosophy that is clearly separated from the roots of the historical memory of humanity tell us that man ought not to imagine that he is something different from all other living beings. And it follows that man ought not to be treated any differently from them.”
— Joseph Ratzinger, 2006, Christianity and the Crisis of Cultures, Ignatius Press, San Francisco.