Greenblatt shows how the Christian obsession with asceticism, suffering and self-righteousness came perilously close to annihilating any traces of a philosophy that eschews the supernatural, and that celebrates life and sees it as worth living and enjoying. It was by sheer chance that an Italian humanist scholar, Gian Francesco Poggio, discovered Lucretius in a palimpsest and started circulating it. In Greenblatt's opinion, the dissemination of this beautiful work of antiquity (measured by the famous thinkers who managed to get their hands on and were inspired by it), may have been one of the leading factors that gave rise to modernity.
In the following audio rendition, read by the inimitable Charlton Griffin, you'll get a sense of the piercing power of Lucretius' philosophy and poetry as he sets down the basics of Epicurus' metaphysical materialism and his fight against the superstitious nature of religion. They say the pen is mightier than the sword, but in Lucretius' hands and with Griffin's god-like and thunderous voice, it's more like a nuclear bomb!
And if you're interested in the text of the above excerpt, you can find a copy here.