The Catholic engaged in the study of natural science is in some ways less well placed than any other student for growing into a full-blooded Christian. His subject is not one which provides obvious stimulation for his Catholic conscience. Its content and presentations are unaltered whether its exponents are Christians or not, and the student lacks the stimulus of that constant need of criticism and re-interpretation, which is provided, for instance, by the study of history. And it is undeniable that natural science when studied intensively easily produces a person hypertrophied in some respects and gravely lacking in Catholic fundamentals. Laboratory work occupies long hours which others would spend on general Catholic reading, and it is too easy to become caught up into a routine which contains little but science. Prayer and spiritual reading do not thrive when they have to be fitted precariously into short intervals saved from the rush. Work is not readily sacrificed to them, for there is severe overcrowding and economic pressure in the lower ranks of scientific workers. (This competition, incidentally, does not favour humility nor a true love of learning.) The manual work of the laboratory gives a certain balance to the scientist’s life, and this again tends to obscure the deficiencies of the latter on the spiritual level. Further, there are certain intellectual obstacles. If a Catholic scientist is intelligent enough to begin thinking about the nature of his scientific knowledge and comparing it with Thomist philosophy, he is liable to be oppressed by certain superficial divergences between the principles of Thomism and of physical science.