“But there are two kinds of sciences. There are those which proceed from the principles known by the natural light of the mind, as arithmetic and geometry. There are others which proceed from principles known by the light of a superior science: as perspective proceeds from principles made known through geometry, and music from principles known through arithmetic. And sacra doctrina is science in this way, because it proceeds from principles known by the light of a superior science or knowledge which is the knowledge belonging to God and the beatified. Thus as music believes the principles delivered to it by arithmetic, so sacred doctrine believes the principles revealed to it from God.”
The question then is raised whether sacra doctrina is one science, or many. And Thomas answers, that it is one, by reason of the unity of its formal object. For it views everything discussed by it as divinely revealed; and all things which are subjects of revelation (revelabilia) have part in the formal conception of this science; and so are comprehended under sacra doctrina, as under one science. Nevertheless it extends to subjects belonging to various departments of knowledge so far as they are knowable through divine illumination. As some of these may be practical and some speculative, it follows that sacred science includes both the practical and the speculative, even as God with the same knowledge knows himself and also the things He makes.
“Yet this science is more speculative than practical, because on principle it treats of divine things rather than human actions, which it treats in so far as man by means of them is directed (ordinatur) to perfect cognition of God, wherein eternal beatitude consists. This science in its speculative as well as practical functions transcends other sciences, speculative and practical. One speculative science is said to be worthier than another, by reason of its certitude, or the dignity of its matter. In both respects this science surpasses other speculative sciences, because the others have certitude from the natural light of human reason, which may err; but this has certitude from the light of the divine knowledge, which cannot be deceived; likewise by reason of the dignity of its matter, because primarily it relates to matters too high for reason, while other sciences consider only those which are subjected to reason. It is worthier than the practical sciences, which are ordained for an ulterior end; for so far as this science is practical, its end is eternal beatitude, unto which as an ulterior end all other ends of the practical sciences are ordained (ordinantur).
“Moreover although this science may accept something from the philosophical sciences, it requires them merely for the larger manifestation of the matters which it teaches. For it takes its principles, not from other sciences, but immediately from God through revelation. So it does not receive from them as from superiors, but uses them as servants. Even so, it uses them not because of any defect of its own, but because of the defectiveness of our intellect which is more easily conducted (manuducitur) by natural reason to the things above reason which this science teaches.”
Thomas now shows, with scholastic formalism, that God is the subjectum of this science; since all things in it are treated with reference to God (sub ratione Dei), either because they are God himself, or because they bear relationship (habent ordinem) to God as toward their cause and end (principium et finem). The final question is whether this science be argumentativa, using arguments and proofs; and Thomas thus sets forth his masterly solution:
“I reply, it should be said that as other sciences do not prove their first principles, but argue from them in order to prove other matters, so this science does not argue to prove its principles, which are articles of Faith, but proceeds from them to prove something else, as the Apostle, in 1 Corinthians xv., argues from the resurrection of Christ to prove the resurrection of us all. One should bear in mind that in the philosophic sciences the lower science neither proves its own first principles nor disputes with him who denies them, but leaves that to a higher science. But the science which is the highest among them, that is metaphysics, does dispute with him who denies its principles, if the adversary will concede anything; if he concede nothing it cannot thus argue with him, but can only overthrow his arguments. Likewise sacra Scriptura (or doctrina or sacred science, theology), since it owns no higher science, disputes with him who denies its principles, by argument indeed, if the adversary will concede any of the matters which it accepts through revelation. Thus through Scriptural authorities we dispute against heretics, and adduce one article against those who deny another. But if the adversary will give credence to nothing which is divinely revealed, sacred science has no arguments by which to prove to him the articles of faith, but has only arguments to refute his reasonings against the Faith, should he adduce any. For since faith rests on infallible truth, its contrary cannot be demonstrated: manifestly the proofs which are brought against it are not proofs, but controvertible arguments.
“To argue from authority is most appropriate to this science; for its principles rest on revelation, and it is proper to credit the authority of those to whom the revelation was made. Nor does this derogate from the dignity of this science; for although proof from authority based on human reason may be weak, yet proof from authority based on divine revelation is most effective.
“Yet sacred science also makes use of human reason; not indeed to prove the Faith, because this would take away the merit of believing; but to make manifest other things which may be treated in this science. For since grace does not annul nature, but perfects it, natural reason should serve faith, even as the natural inclination conforms itself to love (caritas). Hence sacred science uses the philosophers also as authority, where they were able to know the truth through natural reason. It uses authorities of this kind as extraneous arguments having probability. But it uses the authorities of the canonical Scriptures arguing from its own premises and with certainty. And it uses the authorities of other doctors of the Church, as arguing upon its own ground, yet only with probability. For our faith rests upon the revelation made to the Apostles and Prophets, who wrote the canonical books; and not upon the revelation, if there was any, made to other doctors.”[421]
Mediaeval thought was beset behind and before by the compulsion of its conditions. Its mighty antecedents lived in it, and wrought as moulding forces. Well we know them, two in number, the one, of course, the antique philosophy; the other, again of course, the dogmatic Christian Faith, itself shot through and through with antique metaphysics, in the terms of which it had been formulated. These two, very dual and yet joined, antagonistic and again united, constituted the form-giving principles of mediaeval thinking. They were, speaking in scholastic phrase, the substantial as well as accidental forms of mediaeval theology, philosophy, and knowledge. Which means that they set the lines of mediaeval theology or philosophy, and caused the one and the other to be what it became, rather than something else; and also that they supplied the knowledge which mediaeval men laboured to acquire, and attempted to adjust their thinking to. Thus, through the twelfth, the thirteenth, and the fourteenth centuries, they remained the inworking formal causes of mediaeval thought; while, on the other hand, the moving and efficient causes (still speaking in scholastic-Aristotelian phrase) were the human impulses which those formal causes moulded, or indeed suggested, and the faculties which they trained.
The patristic system of dogma with the antique philosophy, set the forms of mediaeval expression, fixed the distinctive qualities of mediaeval thought, furnished its topics, and even necessitated its problems—in two ways: First, through the specific substance which passed over and filled the mediaeval productions; and secondly, simply by reason of the existence of such a vast authoritative body of antique and patristic opinion, knowledge, dogma, which the Middle Ages had to accept and master, and beyond which the substance of mediaeval thinking was hardly destined to advance.