On the Nature of Things is a philosophical work by the Roman author Titus Lucretius Carus (whom we call “Lucretius”). It was written in the early 50s BC, in Latin. Though this is a work of science and philosophy, it is also a poem.

This work provides a detailed description of Epicurean philosophy, which encompasses theories of atoms, cosmology, theology, and a wide variety of natural phenomena. It also addresses the nature of the mind and spirit and promotes the Epicurean lifestyle of pursuing pleasure and avoiding pain. The ultimate purpose of this work as a whole is to dispel the reader’s fears, which come from ignorance, and to show the path to tranquility, which comes from an understanding of the natural world. 

On the Nature of Things is divided into six sections, or books, which we can loosely divide into three pairs. Books I and II deal with the basic principles of atoms. Book I defines atoms and lays out the fundamental laws that govern them. It also addresses the requirements for something to be considered immortal and provides brief introductions to topics that will be covered later, such as astronomy. Book II explores atoms in greater detail, establishing further laws governing their movement and structure.

Books III and IV deal with the mind, the spirit, and the senses. In Book III, Lucretius outlines the rules governing the mind and spirit, and their relation to the body. He makes the key argument that we should not fear death, since it only brings oblivion with no afterlife. Book IV delves deeper into the functions of the mind and body, explaining how the senses work, and examining the role of sex in the Epicurean lifestyle.

Books V and VI examine astronomy, our world, and large-scale natural phenomena. They also attempt to dispel fear of the gods by offering secular explanations for all such things. Book V examines Epicurean cosmology, which places the Earth at the center of a system, with the celestial bodies orbiting around it. This book also establishes the mortality of our entire world. Book VI concludes the work with descriptions of various atmospheric and geological phenomena, as well as pestilence; it provides rational explanations for all these occurrences, rejecting the influence of the gods.

Quotes, line numbers, and page numbers in this guide are based on the following translation:

Smith, Martin Ferguson, translator. On the Nature of Things. By Titus Lucretius Carus, Hackett Publishing Company, 2001.