Copernicus pledged himself, in case his brother's request was granted, to apply during his stay in Italy to the study of medicine also, that he might afterward act as physician to the chapter. The chapter had previously numbered among its members a practical physician, whose death had left in their midst a painful void. From this circumstance it is plain that Copernicus had not as yet received any of the higher orders; nor did he subsequently receive any; for the practice of medicine, including, as it necessarily did, dissecting and searing, constituted an irregularity which debarred from holy orders.
Moreover, Mauritius, Bishop of Ermland, wrote in 1531 that his chapter had but one priest among its members. Copernicus had probably received minor orders only; nor does he mention himself that he ever received any others.
In 1501, with the consent of the chapter, he went to Padua, began the study of medicine, made himself master of Greek, had frequent intercourse with Nicolaus Passara, and Nicolaus Vernia, of the Aristotelian school of philosophy, and, after graduating in medicine, returned to Frauenburg in 1505.
At the episcopal residence of Heilberg he served as private physician to his uncle, and took a lively interest in the extensive projects and undertakings of that prelate. One of these projects was the establishment of a high-school at Elbing. It failed, however, in consequence of the narrow prejudices of the people of that town, who were opposed to having many strangers in their midst The failure of this enterprise is much to be regretted; for without a doubt this institution would have afforded a fine field for the intellectual activity of the great astronomer. His life under these circumstances continued to be simply that of a physician and canonist. His monumental work on the revolutions of the heavenly bodies progressed in secret, according as the ailments of members of the chapter and the lawsuits of Ermland left him leisure for such occupation.
In his case, as in the case of so many others, modesty exhibits itself as the characteristic of genius and true greatness. After the death of his uncle, in 1512, Copernicus returned to Frauenburg, where the residence of the canons on the banks of the Haff, affording an unobstructed view, presented great facilities for astronomical observations. Here he continued to enjoy much popularity as a physician. It must, however, be admitted that a prescription and a regimen sanitatis which we have from him show that he possessed but the limited science of those times. Still he enjoyed the confidence of the people. His brother Andrew, who was afflicted with a species of leprosy, engaged much of his attention.
From 1512 to 1523, Fabian Tettinger was Bishop of Ermland. At his decease, Copernicus was chosen by the chapter as administrator. When he had filled this office for nearly one year, Mauritius Ferber became bishop, and administered the diocese from 1523 to 1537. This prelate, who also was an invalid, placed great reliance on the medical skill of the learned canon.
After his death, Copernicus was associated with three others on the list of candidates for the bishopric. But Dantiscus, Bishop of Kulm, the same who has left the valuable manuscripts for the biography of Copernicus, was nominated. The canon lived on terms of the closest intimacy with this prelate.
At the very beginning of his administration, the new bishop was attacked by a dangerous illness; which, however, the skill of Copernicus succeeded so effectually in relieving, that the bishop was enabled to undertake a long journey as a special envoy. Copernicus rendered effective medical assistance to his friend also, and former classmate, Tiedemann Giese, who in 1538 had been appointed Bishop of Kulm. Tiedemann prevailed on him to dedicate his work on the revolutions of the heavenly bodies to Pope Paul III.; and in return, at the instance of Copernicus, composed a work, entitled Antilogicon, against the errors of Luther; a circumstance which is of decisive significance as regards the religious views of the great astronomer. They lived together thirty years on terms of the most intimate friendship. Duke Albrecht also summoned him to Königsberg to the sick-bed of one of his jurists, notwithstanding that Königsberg boasted several physicians of eminence.
In 1539, Joachim Rheticus, then twenty-six years of age, who had been for two years associated with Luther and Melancthon, came from Wittenberg to Frauenburg to place himself under the tuition of Copernicus. In a work which has not been preserved, he described the impression made on him by the astronomer. There is, however, another production from the same pen, Rhetici Narratio Prima, in which much is said about Copernicus, and which is, consequently, a valuable source of information for his biographer. Rheticus is full of admiration for his instructor. It was he who superintended the publication of the latter's famous work, which appeared at Nuremberg, in 1542. Rheticus repaired to that town expressly for this purpose.
But the last moments of the great scholar were drawing near. After an illness of six months, fortified with the rites of the church, he died on the 24th of May, 1543, yielding up his spirit to Him "in whom is all happiness and every good," as he expresses himself in the preface of his work, the first printed copy of which was placed in his hands on the day of his death.