A common impression prevails that there is serious, if not invincible, opposition between science and religion. This persuasion has been minimized to a great degree in recent years, and yet sufficient of it remains to make a great many people think that, if there is not entire incompatibility between science and religion, there is at least such a diversity of purposes and aims in these two great realms of human thought that those who cultivate one field are not able to appreciate the labors of those who occupy themselves in the other. Indeed, it is usually accepted as a truth that to follow science with assiduity is practically sure to lead to unorthodoxy in religion. This is supposed to be especially true if the acquisition of scientific knowledge is pursued along lines that involve original research and new investigation. Somehow, it is thought that any one who has a mind free enough from the influence of prejudice and tradition to become an original thinker or investigator, is inevitably prone to abandon the old orthodox lines of thought in respect to religion.

Like a good many other convictions and persuasions that exist more or less as commonplaces in the subconscious intellects of a great many people, this is not true. Our American humorist said that it is not so much the ignorance of mankind that makes him ridiculous as the knowing so many things "that ain't so." The supposed opposition between science and religion is precisely an apposite type of one of the things "that ain't so." It is so firmly fixed as a rule, however, that many people have accepted it without being quite conscious of the fact that it exists as one of the elements influencing many of their judgments - a very important factor in their apperception.

Now, it so happens that a number of prominent original investigators in modern science were not only thoroughly orthodox in their religious beliefs, but were even faithful clergymen and guiding spirits for others in the path of Christianity. The names of those who are included in the present volume is the best proof of this. The series of sketches was written at various times, and yet there was a central thought guiding the selection of the various scientific workers. Most of them lived at about the time when, according to an unfortunate tradition that has been very generally accepted, the Church dominated human thinking so tyrannously as practically to preclude all notion of original investigation in any line of thought, but especially in matters relating to physical science. Most of the men whose lives are sketched lived during the fifteenth, sixteenth, and first half of the seventeenth centuries. All of them were Catholic clergymen of high standing, and none of them suffered anything like persecution for his opinions; all remained faithful adherents of the Church through long lives.

It is hoped that this volume, without being in any sense controversial, may tend to throw light on many points that have been the subject of controversy; and by showing how absolutely free these great clergymen-scientists were to pursue their investigations in science, it may serve to demonstrate how utterly unfounded is the prejudice that would declare that the ecclesiastical authorities of these particular centuries were united in their opposition to scientific advance.

There is no doubt that at times men have been the subject of persecution because of scientific opinions. In all of these cases, without exception, however - and this is particularly true of such men as Galileo, Giordano Bruno, and Michael Servetus - a little investigation of the personal character of the individuals involved in these persecutions will show the victims to have been of that especially irritating class of individuals who so constantly awaken opposition to whatever opinions they may hold by upholding them overstrenuously and inopportunely. They were the kind of men who could say nothing without, to some extent at least, arousing the resentment of those around them who still clung to older ideas. We all know this class of individual very well. In these gentler modern times we may even bewail the fact that there is no such expeditious method of disposing of him as in the olden time. This is not a defence of what was done in their regard, but is a word of explanation that shows how human were the motives at work and how unecclesiastical the procedures, even though church institutions, Protestant and Catholic alike, were used by the offended parties to rid them of obnoxious argumentators.

In this matter it must not be forgotten that persecution has been the very common associate of noteworthy advances in science, quite apart from any question of the relations between science and religion. There has scarcely been a single important advance in the history of applied science especially, that has not brought down upon the devoted head of the discoverer, for a time at least, the ill-will of his own generation. Take the case of medicine, for instance. Vesalius was persecuted, but not by the ecclesiastical authorities. The bitter opposition to him and to his work came from his colleagues in medicine, who thought that he was departing from the teaching of Galen, and considered that a cardinal medical heresy not to be forgiven. Harvey, the famous discoverer of the circulation of the blood, lost much of his lucrative medical practice after the publication of his discovery, because his medical contemporaries thought the notion of the heart pumping blood through the arteries to be so foolish that they refused to admit that it could come from a man of common sense, much less from a scientific physician. Nor need it be thought that this spirit of opposition to novelty existed only in the sixteenth and seventeenth centuries. Almost in our own time Semmelweis, who first taught the necessity for extreme cleanliness in obstetrical work, met with so much opposition in the introduction of the precautions he considered necessary that he was finally driven insane. His methods reduced the mortality in the great lying-in hospitals of Europe from nearly ten per cent for such cases down to less than one per cent, thus saving many thousands of lives every year.

Despite this very natural tendency to decry the value of new discoveries in science and the opposition they aroused, it will be found that the lives of these clergymen scientists show us that they met with much more sympathy in their work than was usually accorded to original investigators in science in other paths in life. This is so different from the ordinary impression in the matter that it seems worth while calling it to particular attention. While we have selected lives of certain of the great leaders in science, we would not wish it to be understood that these are the only ones among the clergymen of the last four centuries who deserve an honorable place high up in the roll of successful scientific investigators. Only those are taken who illustrate activity in sciences that are supposed to have been especially forbidden to clergymen. It has been said over and over again, for instance, that there was distinct ecclesiastical opposition to the study of chemistry. Indeed, many writers have not hesitated to say that there was a bull, or at least a decree, issued by one or more of the popes forbidding the study of chemistry. This, is not only not true, but the very pope who is said to have issued the decree, John XXII, was himself an ardent student of the medical sciences. We still possess several books from him on these subjects, and his decree was meant only to suppress pseudo-science, which, as always, was exploiting the people for its own ends. The fact that a century later the foundation of modern chemical pharmacology was laid by a Benedictine monk, Basil Valentine, shows how unfounded is the idea that the papal decree actually hampered in any way the development of chemical investigation or the advance of chemical science.

Owing to the Galileo controversy, astronomy is ordinarily supposed to have been another of the sciences to which it was extremely indiscreet at least, not to say dangerous, for a clergyman to devote himself. The great founder of modern astronomy, however, Copernicus, was not only a clergyman, but one indeed so faithful and ardent that it is said to have been owing to his efforts that the diocese in which he lived did not go over to Lutheranism during his lifetime, as did most of the other dioceses in that part of Germany. The fact that Copernicus's book was involved in the Galileo trial has rendered his position still further misunderstood, but the matter is fully cleared up in the subsequent sketch of his life. As a matter of fact, it is in astronomy particularly that clergymen have always been in the forefront of advance; and it must not be forgotten that it was the Catholic Church that secured the scientific data necessary for the correction of the Julian Calendar, and that it was a pope who proclaimed the advisability of the correction to the world. Down to our own day there have always been very prominent clergymen astronomers. One of the best known names in the history of the astronomy of the nineteenth century is that of Father Piazzi, to whom we owe the discovery of the first of the asteroids. Other well-known names, such as Father Secchi, who was the head of the papal observatory at Rome, and Father Perry, the English Jesuit, might well be mentioned. The papal observatory at Rome has for centuries been doing some of the best work in astronomy accomplished anywhere, although it has always been limited in its means, has had inadequate resources to draw on, and has succeeded in accomplishing what it has done only because of the generous devotion of those attached to it.

To go back to the Galileo controversy for a moment, there seems no better answer to the assertion that his trial shows clearly the opposition between religion, or at least ecclesiastical authorities, and science, than to recall, as we have done, in writing the accompanying sketch of the life of Father Kircher, S.J., that just after the trial Roman ecclesiastics very generally were ready to encourage liberally a man who devoted himself to all forms of physical science, who was an original thinker in many of them, who was a great teacher, whose writings did more to disseminate knowledge of advances in science than those of any man of his time, and whose idea of the collection of scientific curiosities into a great museum at Rome (which still bears his name) was one of the fertile germinal suggestions in which modern science was to find seeds for future growth.

It is often asserted that geology was one of the sciences that was distinctly opposed by churchmen; yet we shall see that the father of modern geology, one of the greatest anatomists of his time, was not only a convert to Catholicity, but became a clergyman about the time he was writing the little book that laid the foundation of modern geology. We shall see, too, that, far from religion and science clashing in him, he afterwards was made a bishop, in the hope that he should be able to go back to his native land and induce others to become members of that Church wherein he had found peace and happiness.

In the modern times biology has been supposed to be the special subject of opposition, or at least fear, on the part of ecclesiastical authorities. It is for this reason that the life of Abbot Mendel has been introduced. While working in his monastery garden in the little town of Brünn in Moravia, this Augustinian monk discovered certain precious laws of heredity that are considered by progressive twentieth-century scientists to be the most important contributions to the difficult problems relating to inheritance in biology that have been made.

These constitute the reasons for this little book on Catholic clergymen scientists. It is published, not with any ulterior motives, but simply to impress certain details of truth in the history of science that have been neglected in recent years and, by presenting sympathetic lives of great clergymen scientists, to show that not only is there no essential opposition between science and religion, but on the contrary that the quiet peace of the cloister and of a religious life have often contributed not a little to that precious placidity of mind which seems to be so necessary for the discovery of great, new scientific truths.

- from Catholic Churchmen in Science, by James J. Walsh, M.D., Ph.D., LL.D., 1906