Kepler, Johann, the celebrated astronomer, deserves a place here not so much on account of his services to the science of astronomy as for the relation he sustained to, and the treatment he received from the Christian Church of the 16th century. He was born near the imperial city of Weil, in Wurtemberg, Dec. 27, 1571, and in his childhood was weak and sickly. He was sent to school in 1577, but the straitened circumstances of his father caused great interruption to his education. He was soon taken from school, and employed in menial services at his father's tavern. In his twelfth year, however, he was again placed at the same school, but in the following year was seized with a violent illness, so that his life was for some time despaired of. In 1586 he was admitted to the monastic school of Maulbronn, where his expenses were paid by the duke of Wurtemberg. The three years of Kepler's life, following his admission to this school were marked by a return of several of the disorders which had well-nigh proved fatal to him in his childhood. To add to his misfortunes, his father left home in consequence of disagreements with his mother, and soon after died abroad. After the departure of his father his mother quarrelled with her relations, "having been treated," says Hantsch, Kepler's earliest biographer, (in his edition of E]pistole ad J. Keplerum, etc. [Leipz. 1718]), "with a degree of barbarity by-her husband and brother-in-law that was hardly exceeded even by her own perverseness." As a natural consequence, the family affairs were in the greatest confusion. Notwithstanding these complications, young Kepler took his degree of master at the University of Tibingen in August, 1591, holding the second place in the examination. While at the university he had paid particular attention to the study of theology, arid no doubt intended to enter the ministry; but, annoyed by the strife which the controversy on the Formula of Concord occasioned, and opposed to the doctrine of ubiquity, at that time made an article in the confession of Wirtemberg's state religion, he failed to secure a position as minister. He now turned to' mathematical studies. His attention was first directed to astronomy by the offer of the astronomical lectureship at Gratz, the chief town of Styria. At that time he knew very little of the subject, but, having accepted the lectureship, he was forced to qualify himself for the position. While engaged in these investigations, he came by degrees to understand the superior mathematical convenience of the system of Copernicus to that of Ptolemy. His general views of astronomy, however, were somewhat mystical, as may be seen in his Prodromus. He supposed the sun, stars, and planets were typical of the Trinity, and that God distributed the planets in space in accordance with regular polyhedrons, etc.
In 1595 Kepler completed his Mysterium Cosmographicum, in which he details the many hypotheses he had successively formed, examined, and rejected concerning the number, distance, and periodic times of the planets, and endeavors to demonstrate the correctness of the Copernican system, which at that time was still discredited and rejected as un-Biblical by both Romanists and Protestants. To avoid persecution, Kepler took the precaution to secure the opinion of eminent theologians of both churches before publication, and for this purpose submitted the MS. to the faculty of Tubingen University. Of course they quickly condemned the sacrilegious effort and daring of the young astronomer (see below), but not so thought duke Louis of Wurtemberg, who not only approved of the work, but furnished the means (in 1596) to defray the expense of printing it. It'must be borne in mind that in the 16th century astronomical truth was equally unknown to the clergy and the laity, and that the motion of the earth and the stability of the sun were doctrines apparently inconsistent with holy Scripture. Besides, in those days the truths of religion were guarded by a sternness of discipline and a severity of punishment which have disappeared in more enlightened times. In order to form a correct judgment respecting the causes which led to the opposition to Kepler by the 'Church, and the subsequent trial and condemnation of Galileo (q.v.), we must turn to that period when they first submitted their opinions to the public. The philosophy of Aristotle was then prevalent throughout Europe. It was taught in all its universities by professors lay and clerical, and every attempt to refute their doctrines exposed its author to the opposition of the learning and scholarship of that day. One of the principal dogmas of the Aristotelian philosophy was the immutability of the heavens. The brilliant discoveries of Kepler and Galileo struck a blow at the ancient philosophy, and consequently exposed them to the hostility of the Peripatetic philosophers. Now when we reflect that the minds of all thinking men were then completely moulded by that philosophy, and that these, again, governed the reflections of those immediately beneath them, and from them the results of Aristoteliamnsm, mingling up, as they did, especially with the religious opinions of the day, thus reached the whole of the popular intellect, we will find it no matter of surprise that the zeal of these innovators met with the most determined opposition. "The Aristotelian professors, the temporizing Jesuits, the political churchmen, and that timid but respectful body who at all times dread innovation, whether it be in legislation or in science, entered into an alliance against the philocophical tyrants who threatened them with the penalties of knowledge." " He who is allowed to take the start of his species," says Sir David Brewster, "and to penetrate the veil which conceals from common minds the mysteries of nature, must not expect that the world will be patiently dragged at the chariot-wheels of his philosophy. Mind has its inertia as well as matter, and its progress to truth can only be insured by the gradual and patient removal of the difficulties which embarrass it." Those Protestants, therefore, who are so ready to 'censure the Church of Rome for its action with regard to these great men should remember that it was but carrying out the spirit of the age, and a measure which the spirit of the people demanded. Surely Protestantism has but little to boast of in this matter. More than half a century later we find that the great and good Sir Matthew Hale condemned to death two women for witchcraft on the ground, first, that Scripture had affirmed the reality of witchcraft; and, secondly, that the wisdom of all nations had provided laws against persons accused of the crime. Sir Thomas Browne, the celebrated author of the Religio Medici, was called as a witness at the trial, and swore "that he was clearly of opinion that the persons were bewitched," Not only so, but Henry More and Cudworth strongly expressed their belief in the reality of witchcraft; and, more than all, Joseph Glauride, probably the most celebrated theological thinker of his time, wrote a special defence of the superstition, without doubt the ablest book ever written on that subject. As late as 1692 nineteen persons were executed and one pressed to death in Massachusetts on the same plea for witchcraft. SEE SALEM. " To deny the possibility, nay, actual existence of witchcraft and sorcery," says Sir William Blackstone (Commentary on the Laws of England, bk. iv. ch. 4:sec. 6), "is at once flatly to contradict the revealed Word of God in various passages both of the Old and New Testaments." SEE WITCHCRAFT.
In 1597 Kepler married Barbara Muller von Muhleckh. She was already a widow for the second time, although two years younger than Kepler himself. In the year following his marriage, on account of the troubled state of the province, arising out of the two great religious parties into which the German empire was then divided, he was induced to withdraw into Hungary. The Jesuits, anxious to secure for the Romish Church the learning and renown of Kepler, earnestly worked in his behalf, and secured permission for his return to Gratz. Very independent in character, Kepler was not the man to eat the bread of his opponents, and upon his frank refusal to join the Romanists he was visited with still fiercer opposition. In 1600 he paid a visit to Tycho Brahe, and, by recommendation of the latter, was appointed assistant imperial mathematician by emperor Rudolph II. Upon the death of Tycho in 1601, Kepler succeeded him as principal mathematician to the emperor, and took up his residence at Prague. The special task intrusted to Kepler at this time was the reduction of Tycho's observations relative to the planet Mars, and to this circumstance is mainly owing his grand discovery of the law of elliptic orbits, and that of the equable description of geras. These continued studies, his searchings after harmony, led him at last to the discovery of the three remarkable truths called Kepler's Laws. (For an account of these, and the steps that led tolheir discovery, see the English Cyclopaedia, s.v. where also will be found a list of Kepler's works.) In 1624 he went to Vienna, the emperor finding it impossible to make good his promises to assist Kepler; to secure the necessary means to aid him in the completion of the Rudolphine Tables; it was not, however, till 1627 that these tables the first that were calculated on the supposition that the planets move in elliptic orbits made their appearance; and it will be sufficient to say of them in this place, that, had Kepler done nothing in the course of his whole life but construct these, he would have well earned the title of a most useful and indefatigable calculator. He died at Ratisbon, Nov. 15, 1630, and his body was interred in St. Peter's churchyard of that city. "Ardent, restless, burning to distinguish himself by his discoveries, he attempted everything; and, having once obtained a glimpse, no labor was too hard for him in following or verifying it. All his attempts had not the same success, and, in fact, that was impossible. Those which have failed seem to us only fanciful; those which have been more fortunate appear sublime. When in search of that which really existed, he has sometimes found it; when he devoted himself to the pursuit of a chimera, he could not but fail; but even there he unfolded the same qualities, and that obstinate 'perseverance that must triumph over all difficulties but those which are insurmountable." See Breitschwerdt, Johann Kepler's Leben u. Wirken (Stuttg. 1831); Brewster, Lives of the Martyrs of Science (Lond. 1841); Bailly, Histoire de l'astronomie moderne, ii, 4 sq.; Bayle, Hist. Diet. s.v.; Aschbach, Kirchen- Lexik . v.; Brockhaus, Converst. Lex. s.v.; English Cyclop. s.v.; Menzel, Gesch. der Deutschen, 5:104 sq., 327 sq., 471; 6:10 sq.