To properly understand the Angelic Doctor’s cathedral of thought, he must be read as a mystic, a theologian, and then only after that – as a philosopher. To enter the cathedral of Aquinas by way of Aristotle, rather than Christ, is to enter the sanctuary incorrectly.
With that being said, I recently stumbled upon this section of an essay by Fr. Cornelio Fabro titled, The Proofs of the Existence of God. In this section Fr. Cornelio identifies a “complement to the five ways” in Aquinas’s biblical commentary on the Gospel of St. John.
“4. Critical Note on the Five Ways
The criticisms inspired by modern thought, though perhaps easier to understand, are not for this reason more satisfying. We can cite, for example, what may be the most common and specious objection: with the five ways, St. Thomas arrives at more than Aristotle’s unmoved Mover, who in fact is not the creator of the world, exercises no Providence regarding humanity, is not personal, etc. – the exact opposite of the Thomistic exegesis. St. Thomas, however, has not simply repeated the Stagirite’s principles, but has penetrated them ‘metaphysically’: in the spiritual climate of Christian creationism he has ‘recovered’ Aristotelian realism’s robust structure of the real, without its historical limitations.
An excellent complement to the five ways is a text which seems to me to be extraordinarily important; later than the Summa, it is still little known even among Thomists.
In the Prologue to his marvelous Lectura in Iohannem St. Thomas shows that philosophers have arrived at God in four ways. He presents them at the beginning of the great commentary on the Gospel of the Word to show how, in its best moments, philosophy was nourished by the Word Himself, turning to Him almost by an inner attraction. I will present their essential content here, as these ‘ways’ can correspond well to the five ways of the Summa, and because the text is unknown and certainly not used by the Thomistic school, though later than the Summa and marvelously explicit.
1) ‘Some attained to a knowledge of God through His authority, and this is the most efficacious way.’ This is the fifth way of the Summan, which here becomes the first: only an Intelligence which transcends the world can explain the finality and order which reigns in the phenomena of nature. ‘For we see the things in nature acting for an end, and attaining to ends which are both useful and certain. And since they lack intelligence, they are unable to direct themselves, but must be directed and moved by one directing them, and who possesses an intellect. Thus it is that the movement of the things of nature toward a certain end indicates the existence of something higher by which the things of nature are directed to an end and governed. And so, since the whole course of nature advances to an end in an orderly way and is directed, we have to posit something higher which directs and governs them as Lord; and this is God.’ The ‘some’ at the beginning of this passage are legion, i.e., all theistic philosophers and indeed all of humanity who, from the order of the world and from the aspirations of man, have always thought of a supreme Orderer to which everything tends and from which all are suspended, the heavens and nature, as Aristotle himself said.
2) ‘Others came to a knowledge of God from His eternity. They saw that whatever was in things was changeable, and that the more noble something is in the grades of being, so much the less it has of mutability. For example, the lower bodies are mutable both as to their substance and to place, while the heavenly bodies, which are more noble, are immutable in substance and change only with respect to place. We can clearly conclude from this that the first principle of all things, which is supreme and more noble, is changeless and eternal.’ This is clearly the way which corresponds most closely to Aristotle’s thought.
Two straightforwardly Platonic ‘ways’ follow; one is in fact attributed to the Platonists, the other to St. Augustine.
3) ‘Still others came to a knowledge of God from the dignity of God; and these were the Platonists. They noted that everything which is something by participation is reduced to what is the same thing by essence, as to the first and highest. Thus, all things which are fiery by participation are reduced by fire, which is such by its essence. And so since all things which exist participate in being (esse) and are beings by participation, there must necessarily be at the summit of all things something which is being (essence) by its essence, i.e., whose essence is its being. And this is God, who is the most sufficient, the most eminent, and the most perfect cause of the whole of being, from whom all things that are participate in being (esse).’ The emphasis and breadth of style show clearly the growing esteem in which St. Thomas held Neoplatonic speculation as the years progressed.
4) ‘Yet others arrived at the knowledge of God from the incomprehensibility of truth. All the truth which our intellect is able to grasp is finite, since according to Augustine, ‘everything that is known is bounded by the comprehension of the one knowing’; and if it is bounded, it is determined and particularized. Therefore, the first and supreme Truth, which surpasses every intellect, must necessarily be incomprehensible and infinite, and this is God.’ The Gospel of St. John gathers these four ways, each the fruit of human ingenuity, into an even greater height and breadth: ‘John’s contemplation was also full. Now contemplation is full when someone is able to consider all the effects of a cause in the cause itself, that is, when he knows not only the essence of the cause, but also its power, according as it can extend out to many things.’ The same can be said of the height and perfection of John’s divine knowledge, such that his Gospel embraces all of the sciences: ‘The Gospel of John contains all together what the above sciences [moral, natural, and metaphysics] have in a divided way, and so it is most perfect.’
It seems beyond doubt that St. Thomas considers all four of these ‘ways’ which today would more properly be called ‘methods’, to be valid and conclusive: he emphasizes arrived at, meaning, ‘they have concluded.’”
– Fr. Cornelio Fabro, The Proofs of the Existence of God –
– Lucas G. Westman
 Selected Words of Cornelio Fabro: Volume 9 God An Introduction to Problems in Theology, Fabro, Pg. 88-90