Dialogo dei massimi sistemi - Galileo’s prohibited text

The item featured here is a first edition of Dialogo dei massimi sistemi (‘Dialogue concerning the two chief world systems’) by Galileo Galilei (1564-1642). The engraved title page reproduced below depicts Aristotle in discussion with Ptolemy and Copernicus.

In this work, Galileo compares the Ptolemaic system with the Copernican system. The Ptolemaic system claimed that the earth was the centre of the universe and had been the accepted view of the earth’s place in the solar system for centuries. Copernicus’ theory, that the earth and other planets orbit the sun, was controversial and when Galileo first published in support of it in 1614 he was accused of heresy. 

Frontispiece showing Aristotle in discussion with Ptolemy and CopernicusIn the 1620s, Galileo was given permission by Pope Urban VIII to publish his theories of the universe, as long as Copernican theory was treated hypothetically.

In 1632, Dialogo dei massimi sistemi was published. The text set out the arguments for and against Copernican theory in the form of a debate between three men – one Copernican, a follower of Ptolemy and a mediator who guided the discussion. Readers found that the Copernican argument was the stronger of the two and that the Ptolemaic supporter had been named simplicio (‘simpleton’ in Italian).

Pope Urban VIII ordered that no more copies were to be published and Galileo was accused of heresy once again. In 1633 he was summoned before the Inquisition in Rome and the text was put on the Index of Prohibited Books. Galileo was forced to retract his support of Copernican theory and was sentenced to permanent house arrest.

Dialogo dei massimi sistemi remained on the Index of Prohibited Books for 111 years, before a heavily censored version was released in 1744. The full text was published again in 1835, 202 years after it had been banned.

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