An alchemist’s illuminated manuscript opens to a page we know well. A figure stands with two heads, one male, one female, each crowned by a sun and a moon. In one hand it holds a compass, in the other a philosopher’s egg. The body is neither man nor woman. It is the Rebis, the “thing of two,” the completed stone of the wise. A few pages later, a different image: a tiny human, fully formed, sealed inside a glass gourd, nourished by a drop of blood. That is the Homunculus, the artificial man. Both are products of the alchemical opus, but they answer different questions. The Rebis asks: what happens when opposites are perfectly united? The Homunculus asks: can life be made from base matter by human hands?
What Exactly Are the Rebis and the Homunculus?
The Rebis (Latin for “two things” or “thing of two”) is the hermaphroditic being that appears at the end of the alchemical conjunctio — the stage where sulfur and mercury, sun and moon, male and female are fused into a single substance. It is not a separate creature. It is the philosopher’s stone itself, in symbolic form, before it is projected onto base metal. The Rebis is the proof that the operation has succeeded.
The Homunculus (Latin for “little man”) is a different ambition. In the 1537 treatise De Natura Rerum, the Swiss physician and alchemist Paracelsus (c. 1493–1541) described a method for creating a living human being without a womb. The procedure: seal human sperm in a glass gourd, bury it in horse dung for forty days (the heat of putrefaction), then nourish the resulting translucent form with human blood for another forty weeks. The result is a child-sized human, intelligent, powerful, and capable of living for a century without illness.
One is a symbol of completion. The other is a recipe for a new body.
Where Did These Ideas Come From?
The Rebis first appears in the printed alchemical literature of the sixteenth century. The most famous illustration is from the Rosarium Philosophorum (1550), a German anthology of alchemical texts. In that woodcut, the Rebis stands atop a dragon biting its own tail (the ouroboros), holding a compass and an egg. The two heads signify the double nature of the stone: both fixed and volatile, both spiritual and material. The image becomes a staple of later emblem books, such as the Atalanta Fugiens (1617) of Michael Maier (1568–1622).
The Homunculus is older in its echoes but fixed in its form by Paracelsus. Earlier alchemists, including Zosimos of Panopolis (c. 300–400 CE), described visions of a “little man” inside the furnace, a shape that appeared during the whitening stage. But Zosimos called it a vision, not a recipe. Paracelsus turned it into a laboratory procedure. In his De Natura Rerum, he writes that the homunculus can be raised to full adulthood without the intervention of a woman, and that it “knows all secret arts.”
That claim mattered. It meant that the alchemist, by imitating nature, could bypass nature. The homunculus was not a symbol. It was a challenge to the limits of generation.
What Do They Mean?
The Rebis is the alchemical coincidentia oppositorum — the coincidence of opposites. The two heads, the two genitals, the sun and moon, the red and white: every dualism collapsed into one body. For the alchemist, this was the goal of the Great Work. The soul and the body reconciled. The fixed and the volatile married. The Rebis is the stone, but it is also the perfected human, the homo maximus who contains all things.
The Homunculus carries a different symbolism. It is the microcosm — the little world that mirrors the macrocosm. Paracelsus believed that each human being was a miniature cosmos, and that the homunculus, being generated artificially, was a pure product of the four elements and the astral influences. The homunculus is also a symbol of the alchemist’s power to create life from putrefaction. It is the ultimate proof that the art can imitate the Creator.
But there is a darker side. The homunculus, in later folklore, becomes a creature of servitude, a golem-like being bound to its maker. The Rebis never serves. It is the stone. It is the end.
How Were They Practically Understood?
The Rebis was not made. It was achieved. The alchemist did not assemble a two-headed body. Instead, he worked through the stages of the opus, nigredo, albedo, citrinitas, rubedo, and the Rebis appeared in the final white-to-red transition. It was the moment when the stone was ready to multiply. The Rosarium Philosophorum describes the Rebis as the “body of the stone that has been made one.” The practical work was the purification of mercury and sulfur, the repeated destillation and cohobation, until the red stone emerged.
The Homunculus, by contrast, was a precise laboratory recipe. Paracelsus’s instructions are specific: human sperm in a sealed vessel, horse dung for heat, forty weeks of blood feeding. Later alchemists, including Johann Konrad Dippel (1673–1734), claimed to have attempted the procedure. Dippel, who also worked with bone oil and animal magnetism, was rumored to have created a homunculus, though no evidence survived. The recipe was taken seriously into the eighteenth century. In 1775, the Swedish chemist Torbern Bergman (1735–1784) wrote a paper on the possibility of artificial generation, citing Paracelsus.
The two beings were never made in the same way. The Rebis was the goal of the opus. The Homunculus was a separate operation, a side project of the art.
Rebis vs Homunculus: Key Comparisons
| Aspect | Rebis | Homunculus |
|---|---|---|
| First appearance | Rosarium Philosophorum (1550) | De Natura Rerum (1537) |
| Method | The conjunctio stage of the opus | Putrefaction of sperm in a gourd |
| Scale | Symbolic, diagrammatic | Practical, laboratory recipe |
| Purpose | The philosopher’s stone completed | A living human without a womb |
| Gender | Hermaphroditic (two heads, two sexes) | Typically male (Paracelsus does not specify female) |
| Immortality | The stone is incorruptible | The homunculus is mortal but long-lived |
| Modern influence | Jungian psychology, alchemical symbolism | Literature (Mary Shelley’s Frankenstein), esoteric transhumanism |
The Rebis has no practical recipe. It is the result of the entire opus. The Homunculus has a recipe but no verified success.
What People Get Wrong
One common error is to treat the Rebis as a monster. It is not. The two heads are not a deformity. They are the visible sign of the union of opposites. Medieval and Renaissance alchemists did not see the Rebis as grotesque. They saw it as the most perfect form.
Another mistake is to assume the homunculus is a medieval invention. It is not. The earliest clear recipe is Renaissance, Paracelsus’s 1537 text. The word does appear in medieval alchemy, but it refers to a spiritual vision, not a biological creation.
A third confusion: the Rebis and the homunculus are sometimes treated as interchangeable. They are not. The Rebis is the stone. The Homunculus is a living being. The Rebis is the goal of the work. The Homunculus is a product of one specific procedure. An alchemist who had made the Rebis would not need to make a homunculus. The stone could do everything.
FAQ
Can you actually make a Rebis?
No, because the Rebis is not a physical object. It is the symbolic representation of the completed philosopher’s stone. The stone itself could be made, but the Rebis as a two-headed figure is an emblem, not a recipe.
Did anyone ever make a homunculus?
Paracelsus claimed it was possible, and Johann Konrad Dippel later claimed to have succeeded, but no verifiable record exists. The procedure is not reproducible by modern biology.
Is the homunculus the same as the philosopher’s stone?
No. The homunculus is a living being. The philosopher’s stone is a mineral substance that transmutes metals. Some alchemists linked the two, but they are distinct operations.
Why are both often depicted as androgynous?
Only the Rebis is consistently androgynous. The homunculus is usually male. The Rebis is androgynous because it represents the union of opposites, which was the core of the alchemical coniunctio.
The Rebis and the Homunculus are two answers to one question: what can alchemy make? The Rebis says: the perfect unity of all things. The Homunculus says: a new life. Both are products of the same art, but they point in different directions, one toward the stone, the other toward the flesh. To understand the alchemical tradition, you need to hold both in your mind: the two-headed symbol of completion and the small man in the gourd, waiting for blood.
For further reading, explore our complete guide to alchemy, the glossary of alchemical symbols, and the Guides to the Philosopher’s Stone.