Epicurus was a very serious person and his work, now lost, may have been hard going. He was fortunate that Lucretius was later able to explain Epicureanism in an accessible way. His six volumes of poetry now rank as outstanding pieces of literature in Latin. You might have the greatest idea ever thought up, but if you cannot popularize it you are lost. It was the role of Lucretius to elucidate the ideas of the great philosopher.
De rerum natura deals with atomism, nature, the universe, the body and the soul. Everything, he says, can be explained by natural laws, not by superstition or the intervention of over-active gods. The idea gods waft around Mount Olympus but don’t create universes or concern themselves with our lives. The soul dies with the body. Death is natural and not to be feared, for we and our atoms are all re-cycled in the grand scheme of things. Mankind has free will. Earthquakes and sicknesses are not caused by witchcraft. People become sick from natural causes. Nothing can be produced from nothing, and nothing can be reduced to nothing. The planets and space have their origin in an infinite number of atoms in a great void, swerving, joining together, making new planets. The sun and moon, day and night, the seasons and natural calamities all obey a set of natural laws.
The work of Lucretius was anathema to the early Christian church, which effectively discredited him. Even today he doesn’t get the respect he deserves. The more one knows about the early christian church, its politics, power moves and intolerance, the more one values the calm, studied rationality of Epicurus.
The real importance of Lucretius lies in the fact that his work survived until modern times, since most Epicurean writings were deliberately destroyed. He and Epicurus (with a bow to Democritus before him) are responsible for helping to lay a foundation for the work of more scientifically proficient men during the Renaissance and Enlightenment.
The explosion, or revolution, that is scientific progress since the time of Galileo and Newton had one of its origins in the Garden. I say “one of its origins” because, for instance, a century before De rerum natura was rediscovered, men like William of Ockam and Francis Bacon were already applying scientific methods to the natural world. Lucretius was re-discovered at an opportune moment.