De Homine

Hobbes intended a trilogy: De Corpore (on body and physics), De Homine (on human nature), and De Cive (on citizenship and politics) . The order of composition was reversed—De Cive appeared in 1642, De Corpore in 1655, and De Homine in 1658, when Hobbes was seventy . De Homine's function is to bridge the physics of matter in motion to the political theory of the commonwealth. It must explain how human beings, as bodies subject to the same laws as all matter, come to have sensations, appetites, language, and the passional structure that makes politics necessary. One scholarly assessment notes that the transition in De Homine from human physiology to customs and religion is a meeting 'almost like a precipice' of materials already written, rather than a fully integrated bridge .

Hobbes's optics in De Homine argue that vision is not a passive reception of images but an active reaction of the sense organ. When light strikes the retina, the eye responds with a 'conatus'—an imperceptible motion that sweeps along the optical axis to produce an image that is 'ordered, upright, and not inverted' . This contrasts with Descartes, who located the formation of visual images in the pineal gland and the immaterial soul. For Hobbes, the entire process is physical: the reaction of the organ is itself the sensation. This is crucial because it demonstrates that even the most refined human experience—sight, the 'noblest of the sciences'—can be explained without appeal to incorporeal substances. The optics of De Homine are thus not a digression but a proof of concept for Hobbes's materialism.

In the preface, Hobbes explains the delay with a striking self-comparison: he says he has 'fought with wild beasts' (ἐθηριομάχησα), a phrase borrowed from Paul's first letter to the Corinthians . The reference is likely metaphorical, casting Hobbes as an apostle of truth struggling against heretical opponents who resisted his message. The delay was not merely technical but polemical: Hobbes had been embroiled in controversy since Leviathan, and the completion of his philosophical system was hampered by the need to defend his positions. The preface also admits that much of De Homine's material was written years earlier, and that Hobbes no longer felt the same enthusiasm for the project, publishing it out of a sense of obligation to complete the trilogy .

De Homine and Leviathan overlap in their treatment of sensation, imagination, speech, and the passions, but De Homine is more detailed on physiology, particularly optics. Where Leviathan is a political treatise that incorporates psychology as needed, De Homine is a systematic physiology of the human being as a natural body. It includes eight chapters on language, attraction and aversion, the passions, and religion, but the optical sections are its most original contribution . The relationship between the two works is not one of supersession. De Homine shows Hobbes working out the physicalist foundations of his psychology with a technical precision that Leviathan does not attempt. Readers who know Hobbes only through Leviathan will find here the mechanistic substrate that makes the political theory intelligible.

De Homine was first published in Latin in 1658. It was translated into German in 1918 (except for the optical part) and into Italian in 1970 . The first English translation appeared in 1972, in Man and Citizen, translated by Charles T. Wood, T.S.K. Scott-Craig, and Bernard Gert, and edited with an introduction by Bernard Gert . This edition was reprinted by Hackett Publishing in 1991 with corrections . The translation is generally well regarded, though one reviewer noted that a critical edition and a scholarly analysis of De Homine's role in the optical revolution of the seventeenth century was still wanting . The Hackett edition remains the standard English text and is widely available.

The distinction matters because De Homine is deliberately both, and reading it as one or the other misses its function in Hobbes's system. It is a work of natural science—physiology, optics, psychology—but it is written in the service of politics. Hobbes's trilogy is designed to show that the commonwealth can be derived from the nature of human beings as bodies in motion. De Homine supplies the account of that nature. Without it, De Cive's claims about human passions and the need for sovereignty lack their physical foundation. The book is thus political philosophy conducted through natural science, or natural science undertaken for political ends. Readers who approach it expecting either a political treatise or a neutral scientific text will find something more ambitious: a unified system in which physics, anthropology, and politics are continuous.