From Zenit:
The Enlightenment had taken the idea of progress as
its leitmotiv, preaching a secular humanism that would usher in an age
of reason, where religion would be replaced by science.
Nineteenth-century ideologies built on many of the aspects of the Enlightenment...Add to the mix Hegel's philosophy of dialectical progress, and we had the perfect setup for the tragic totalitarian experiments of
the 20th century, which sought to bring about an earthly paradise
without God. By excluding God, they also wound up trampling on the
human person as well.
Q: How does the Christian idea of progress differ from these ideologies?
For more depth, the encyclical itself.

Comments