The topic propounded here is so vast that we must be permitted to choose a few of its aspects and omit the rest. We are concerned with the position of Catholic theology in regard to the scientific doctrine, opinion, hypothesis or theory of "hominisation", that is, of man's evolutionary origins, as far as these come within the scope and methods of the natural sciences. But we must in the first place leave aside the question of what is termed monogenism. An adequate discussion of that problem would require a Quaestio Disputata to itself.1 Furthermore, the philosophical aspects of the subject must also largely be left out of account, though they are very relevant and important and cannot entirely be avoided. But a philosophical treatment really adequate to the metaphysics of the case would demand a much more comprehensive work than can be attempted here. What is offered, as far as philosophy is concerned, is a few rather arbitrarily selected reflections such as a theologian must undertake if he is in some degree to deal with his own set of problems. There are, of course, questions which are prior in principle to the empirical sciences and which are presupposed to an objective and adequate statement of the problems of a possible real connection between man and the animal kingdom. Such, for example, are those concerning the nature of natural science in general; and the epistomological priority of a metaphysical account of man over the empirical, a posteriori sciences by reason of the knowledge it gives of man's fundamental and unchanging essence. Then there are questions regarding the nature of mind and matter as such, the concepts of becoming, and of unchanging natures, the philosophical question of the nature of the substantial soul and its relation to the body. All these themes cannot, unfortunately, be expressly dealt with in a discussion which is in intention a purely theological one.
Another brief preliminary observation may be permitted on the content and arrangement of the essay. Because it is fundamentally theological in character, scientific data and problems are not the real subject; they serve simply as a guide in selecting the perspectives in which the theological matter is envisaged. Nor can the theology of man be expounded in its entirety, but only in so far as it is of importance for a Catholic scientist in relation to the theory of human evolution.
The theme thus delimited will be treated in three stages. First, a summary of the official pronouncements of the Church on questions regarding man and his nature. It is best to have this at the beginning, because the authoritative teaching of the magisterium is always the most immediate source and the first and last normative principle of a Catholic theology. It is also preferable on practical apologetic grounds, for a Catholic scientist will certainly want to hear the official teaching of the Church and not the private theological opinions of an individual theologian. It is, after all, the relation between scientific theories and the official teaching of the Church that decides the question whether a scientist has difficulties in being a Christian believer and a Catholic.
The exposition of the official teaching of the Church leaves open, of course, many questions which urgently call for an answer if the fundamental problem of the relation between a theology of Revelation and scientific theories of evolution is to be cleared up. Consequently the attempt is made in a second section to grapple more radically with the matter. With the Bible directly in view, the question is raised, what exactly Revelation does fundamentally intend to assert about man and his origins. In that way it is possible to answer the question whether a conflict between a theological and a scientific account of man is even really particularly likely. What is meant by this, and how this second topic is to be handled, must be left to emerge more clearly in the second section itself.
Finally, a few of the questions at least which the first two sections gave rise to but left open, must be submitted to rather more systematic reflection. For it will be seen, particularly in the first section, that even the Church's official permissive toleration of a moderate theory of evolution still leaves many questions unanswered, and in fact raises new problems. It is true that these questions link up with very general and fundamental problems of a philosophical and theological doctrine of man, and with problems of natural philosophy in its widest sense. Consequently it cannot be expected that they will be cleared up here in a precise, detailed and satisfactory manner. But the hope and justification of the reflections offered in the third section is, that even a small advance towards an answer, and the clearer recognition of what exactly must still be open to question, is useful and important. What precisely the questions are that must be raised, will more suitably be shown in the third section itself.
1 Cf. on this, K. Rahner, "Theologisches zum Monogenismus" in Schriften zür Theologie I (Einsiedeln'1964) pp. 253-322. English translation, Theological Investigations Vol. I, (London 1961) pp. 229-96.