Signatura rerum: nature as a book of signs

An ancient image, widespread since the Church Fathers, held that God had written two books: Scripture and nature. The first was read through theology, the second through the observation of creation. In the Renaissance this metaphor took on a surprisingly literal meaning. For many philosophers and physicians the things of the world bear visible signs impressed upon them, “signatures”, which reveal their hidden virtues to those who know how to read them. This is the doctrine of signatura rerum, the signature of things.

The book of nature

Augustine, in his commentary on the Psalms and in other writings, invited readers to read creation as a page open to all, even to those who could not read. In the twelfth century Hugh of Saint Victor compared the sensible world to a book written by the finger of God, and Alan of Lille composed verses in which every creature is for us like a book and a picture. This tradition made it natural to seek in phenomena a message to be interpreted.

Cornelius Agrippa stands within this vision. In the first book of De occulta philosophia he states that the occult virtues of things can sometimes be recognised from outward signs, such as shape, colour or resemblance to other realities. The stars, according to the philosopher, imprint upon things characters and figures that reveal their belonging to a particular planet.

Paracelsus and the doctrine of signatures

The Swiss physician Theophrastus Bombastus von Hohenheim, known as Paracelsus, who lived from around 1493 to 1541, gave the theory its most influential formulation. According to him nothing in nature is without a sign: nature has marked everything so that man may recognise its use. His follower Oswald Croll published in 1609 the Tractatus de signaturis internis rerum, and the Neapolitan Giambattista Della Porta had already devoted the Phytognomonica of 1588 to the subject.

The examples most often cited by tradition concerned plants: the walnut, whose kernel resembles the brain, was associated with the head; eyebright, with a flower that looks like an eye, with the eyes. These associations, today devoid of any scientific foundation, show a method of reasoning by analogy that dominated learned herbalism for centuries and that modern botany and medicine have abandoned.

Böhme, Galileo and the language of the world

The German mystic Jakob Böhme, a shoemaker from Görlitz, wrote in 1622 a treatise known by the Latin title De signatura rerum. For him the signature is not merely an outward form, but the expression of the inner essence of each thing, its own voice. Every being manifests outwardly what it is inwardly, and the whole of nature becomes a language to be understood spiritually.

A year later, in The Assayer of 1623, Galileo Galilei took up the ancient metaphor with an entirely different meaning: the great book of the universe, he wrote, is “written in the language of mathematics”. The book of nature remained open, but its characters were no longer resemblances and signatures, but triangles, circles and geometrical figures.

Between Agrippa and Galileo, then, a decisive transition in the history of knowledge takes place. The signatura rerum represents the last great attempt to read nature as a symbolic text, rich in analogies and correspondences. Knowing it helps us understand not only Renaissance magic, but also the way modern science redefined the very meaning of “reading” the world.