The attitude of Dutch Roman Catholics towards the natural sciences in the second half of the nineteenth century In the second half of the nineteenth century there were no Roman Catholic professors in the natural sciences at the Dutch universities. Original contributions to the natural sciences from Roman Catholic scholars are lacking. In fact the natural sciences had a bad reputation among Roman Catholics, because they were considered as materialistic and positivistic, both condemned by Pope Pius IX. In Roman Catholic periodicals, in which apologetics was the main programme, it was stated that it is impossible that the Church can harm the development of natural science. Therefore the attitude of the Church towards the copernican world view and towards darwinism was defended. Only at the end of the century a first change set in with the encyclical letter Aeterni Patris (1879) in which the philosophy of Thomas Aquinas - which was more favourable towards modern natural science - was prescribed for the seminary. In 1904 a 'society for the promotion of the study of science among Roman Catholics in the Netherlands' was founded. This society - since 1947 the Thijmgenootschap - became a strong stimulus for scientific activities among Dutch Roman Catholics in this century.