Heydon was famous as a champion of
astrology. His best-known work was
A Defence of Judiciall Astrologie (1603), the most substantial English defence of astrology of its day, rebutting
John Chamber's
A Treatise Against Judiciall Astrologie (1601), which had called for parliament to outlaw astrology. Heydon argued that it was a valid science, compatible with Christianity. He drew upon
Tycho Brahe and others. Heydon also wrote but did not publish
An Astrological Discourse with Mathematical Demonstrations (c. 1608), a further defence of astrology drawing on
Kepler, with a short account of the 1603 conjunction of
Saturn and
Jupiter. The manuscript passed to the astrologer
Nicholas Fiske, whose attempts to publish it failed, but it appeared in an edited form in 1650, subsidised by
Elias Ashmole, with a preface by
William Lilly. Heydon's work was given weight by his social standing and the lack of challenges to it. No reply by Chamber appeared, and
George Carleton's
The Madnesse of Astrologers (1624) was published only twenty years later. Heydon also made elaborate predictions for 1608 and 1609, which remained unpublished.
Bibliography •
A Defence of Judiciall Astrologie by Christopher Heydon (1603) •
An astrological discourse with mathematical demonstrations, proving the powerful and harmonical influence of the planets and fixed stars upon elementary bodies, in justification of the validity of astrology. Together with an astrological judgment upon the great conjunction of Saturn & Jupiter 1603, Written by that worthy learned gentleman Sir Christopher Heydon, Knight, and now published by Nicholas Fiske, Jatromathematicus [c. 1608, first published 1650] •
Astrology: The wisdom of Solomon in miniature, being a new doctrine of nativities... or, the art of determining future events by Christopher Heydon •
The new astrology, or, The art of predicting or foretelling future events by the aspects, positions, and influence of the heavenly bodies: founded on scripture, experience, and reason... in two parts by Christopher Heydon ==Predictions==