Little is known of the life of Bernard of Verdun, except that he was a Franciscan

Franciscan

Most Franciscans are members of Roman Catholic religious orders founded by Saint Francis of Assisi. Besides Roman Catholic communities, there are also Old Catholic, Anglican, Lutheran, ecumenical and Non-denominational Franciscan communities....

 friar

Friar

A friar is a member of one of the mendicant orders.-Friars and monks:...

 who may have been born in Verdun

Verdun

Verdun is a city in the Meuse department in Lorraine in north-eastern France. It is a sub-prefecture of the department.Verdun is the biggest city in Meuse, although the capital of the department is the slightly smaller city of Bar-le-Duc.- History :...

 and lived in the second half of the thirteenth century. His most significant work was the Treatise on the Whole of Astronomy (Tractatus super totam astrologiam), in which he defended Ptolemy's

Ptolemy

Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

 theory of epicycles and eccentrics

Deferent and epicycle

In the Ptolemaic system of astronomy, the epicycle was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets...

 against al-Bitruji's system of homocentric spheres. Contrary to the criticisms of Averroes

Averroes

' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

 and al-Bitruji, Bernard maintained that Ptolemy's theory was consistent with Aristotle's physics

Aristotelian physics

Aristotelian Physics the natural sciences, are described in the works of the Greek philosopher Aristotle . In the Physics, Aristotle established general principles of change that govern all natural bodies; both living and inanimate, celestial and terrestrial—including all motion, change in respect...

. He further pointed out many technical inadequacies of al-Bitruji's model, and considered it to be insufficiently developed to challenge Ptolemy's system.