Remembering a Jesuit math whiz

This year marks the four hundredth anniversary of the death of Christopher Clavius, the great Jesuit mathematician. He was a contemporary of Copernicus and Galileo, and lived from 1537 to 1612.

Clavius, who signed his 23 books Clavius Bambergensis, after his birthplace in Bamberg, was received into the Society of Jesus by St Ignatius in 1555 and studied in Coimbra , Portugal, where he observed an eclipse of the sun, a portent of his later interest in astronomy. He became the Professor of Mathematics at the Jesuit Roman College in 1567 and held the chair until 1595.  After his retirement he revised his publications and focused his attention on astronomy.

Clavius’ great work lay in the teaching of mathematics. At the Roman College he fostered good scholars who went on to teach in the Jesuit Colleges throughout Europe. He published several manuals for teaching mathematics and wrote commentaries on the geometry of Euclid and Theodosius.

He came to public notice, however, with the reform of the calendar. The Julian calendar, prescribed for the Roman Empire by Julius Caesar in 45 BC, was current though Western Europe. But it was inaccurate, and the inaccuracies affected the dating of the spring equinox, and consequently of Easter. Gregory XIII commissioned a reform of the calendar and proclaimed it in 1582.

Clavius was given the task of explaining and defending the reform. This was a delicate task, because the reform meant that 10 days would be lost from the calendar in 1582. Such theft of time from people’s lives could cause riots. Some Protestant critics also saw the reform as an abuse of papal power.  Clavius published three books explaining and defending the reform.

This work focused his increasing interest in astronomy. One of his earlier books had been a commentary on the astronomical synthesis of an English thirteenth century teacher, Johannes Sacrobosco (John Holywood to his friends). This was based on the authoritative work of Ptolemy, a second century scholar from Alexandria. Clavius remained convinced of Ptolemy’s argument that the earth was the centre of the universe, and that other heavenly bodies revolved around it.  But although not persuaded by the heliocentric thesis of Copernicus, he was impressed by his arguments, as he was by the discoveries of Galileo. He saw the need for a reformed astronomical theory.

In this Clavius was true to his fundamental insight, that science needed to be founded on mathematics and on experiment, not simply on deduction and on ancient authorities. In this respect he was part of the beginnings of modern science. And his position provokes one of the great unresolvable ‘what ifs’ of Jesuit and European cultural history.

Clavius worked to persuade other Jesuits of the importance of mathematics in the educational curriculum.  In a draft revision of the Ratio Studiorum, the curriculum for Jesuit studies, he proposed that mathematics should be made central within the teaching of philosophy in Jesuit Colleges. He also proposed that the lack of good teachers should be remedied by a specialist academy for the training of gifted Jesuit mathematicians. 

The response to the draft was that the lack of good teachers made the proposal unworkable. The final draft was simply aspirational in its general commendation of mathematics. At a time when the Jesuit Colleges played such an important part in higher education and culture in Europe, one wonders what would have been the effect of making mathematics a central part of their curriculum. Might the gaps that developed between church and science, and between metaphysics and the common scientific world view, have become so neuralgic?

Clavius made a key contribution to his age, but some doors even he was unable to unlock.

By Andy Hamilton SJ