Johannes Kepler had become mathematician to the states of Upper Austria in 1612.

Ursula Reingold, a woman in a financial dispute with Kepler's brother Cristoph, had in 1615 claimed Kepler's mother Katharina had made her sick with an evil brew.

The dispute had escalated, and Katharina had in 1617 been accused of witchcraft; witchcraft trials are relatively common in central Europe at this time.

Beginning in August 1620, she had been imprisoned for fourteen months.

She is released in October 1621, thanks in part to the extensive legal defense drawn up by Kepler.

The accusers had no stronger evidence than rumors, along with a distorted, secondhand version of Kepler's Somnium, in which a woman mixes potions and enlists the aid of a demon.

However, Katharina had been subjected to territio verbalis, a graphic description of the torture awaiting her as a witch, in a final attempt to make her confess.

Throughout the trial, Kepler had postponed his other work to focus on his "harmonic theory".

The result, published in 1619, was Harmonices Mundi ("Harmony of the Worlds"), in which Kepler discusses harmony and congruence in geometrical forms and physical phenomena.

The final section of the work relates his discovery, in 1618, of the so-called "Third Law" of planetary motion.