The relationship between the Catholic Church and science is a widely debated subject. Historically, the Catholic Church has often been a patron of sciences. It has been prolific in the foundation of schools, universities and hospitals, and many clergy have been active in the sciences. Historians of science such as Pierre Duhem credit medieval Catholic mathematicians and philosophers such as John Buridan, Nicole Oresme, and Roger Bacon as the founders of modern science. Duhem found "the mechanics and physics, of which modern times are justifiably proud, to proceed by an uninterrupted series of scarcely perceptible improvements from doctrines professed in the heart of the medieval schools." Yet, the conflict thesis and other critiques emphasize historical or contemporary conflict between the Catholic Church and science, citing in particular the trial of Galileo as evidence. For its part, the Catholic Church teaches that science and the Christian faith are complementary, as can be seen from the Catechism of the Catholic Church which states in regards to faith and science:
Though faith is above reason, there can never be any real discrepancy between faith and reason. Since the same God who reveals mysteries and infuses faith has bestowed the light of reason on the human mind, God cannot deny himself, nor can truth ever contradict truth. ... Consequently, methodical research in all branches of knowledge, provided it is carried out in a truly scientific manner and does not override moral laws, can never conflict with the faith, because the things of the world and the things of faith derive from the same God. The humble and persevering investigator of the secrets of nature is being led, as it were, by the hand of God in spite of himself, for it is God, the conserver of all things, who made them what they are.
Catholic scientists, both religious and lay, have led scientific discovery in many fields. From ancient times, Christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals and the Church remains the single largest private provider of medical care and research facilities in the world. Following the Fall of Rome, monasteries and convents remained bastions of scholarship in Western Europe and clergymen were the leading scholars of the age – studying nature, mathematics, and the motion of the stars (largely for religious purposes). During the Middle Ages, the Church founded Europe's first universities, producing scholars like Robert Grosseteste, Albert the Great, Roger Bacon, and Thomas Aquinas, who helped establish the scientific method.
This view of the Church as a patron of sciences is contested by some, who speak either of an historically varied relationship which has shifted, from active and even singular support, to bitter clashes (with accusations of heresy) – or of an enduring intellectual conflict between religion and science. Enlightenment philosophers such as Voltaire were famously dismissive of the achievements of the Middle Ages. In the 19th century, the "conflict thesis" emerged to propose an intrinsic conflict or conflicts between the Church and science. The original historical usage of the term asserted that the Church has been in perpetual opposition to science. Later uses of the term denote the Church's epistemological opposition to science. The thesis interprets the relationship between the Church and science as inevitably leading to public hostility, when religion aggressively challenges new scientific ideas as in the Galileo Affair. An alternative criticism is that the Church opposed particular scientific discoveries that it felt challenged its authority and power – particularly through the Reformation and on through the Enlightenment. This thesis shifts the emphasis away from the perception of the fundamental incompatibility of religion per se and science-in-general to a critique of the structural reasons for the resistance of the Church as a political organisation.
The Church itself rejects the notion of innate conflict. The Vatican Council (1869/70) declared that "Faith and reason are of mutual help to each other." The Catholic Encyclopedia of 1912 proffers that "The conflicts between science and the Church are not real," and states that belief in such conflicts are predicated on false assumptions.Pope John Paul II summarised the Catholic view of the relationship between faith and reason in the encyclical Fides et Ratio, saying that "faith and reason are like two wings on which the human spirit rises to the contemplation of truth; and God has placed in the human heart a desire to know the truth – in a word, to know himself – so that, by knowing and loving God, men and women may also come to the fullness of truth about themselves." The present Papal astronomer Brother Guy Consolmagno describes science as an "act of worship" and as "a way of getting intimate with the Creator."