The Necessity of Reason
While faith and reason are, particularly since the so-called Renaissance and Enlightenment, often treated as diametrically opposed and mutually exclusive, in truth they derive from the same faculty of the human person, that power of our souls which distinguishes us as being made in “the image of God” (Gn 1:27 DRA): the intellect.
Contrary to its popular modern understanding as a kind of neurological computer analyzing information in a purely detached, dry way, from the time of Socrates the intellect has been understood as the capacity to recognize and understand truth. This naturally raises, then, especially in our relativistic age, the same question which Pontius Pilate once posed to Jesus: “What is truth?” (Jn 18:38) St. Thomas Aquinas can help us here. He defines truth as
in the intellect in so far as it is conformed to the object understood, the aspect of the true must needs pass from the intellect to the object understood, so that also the thing understood is said to be true in so far as it has some relation to the intellect. (ST I, q. a, a. 1)
This statement, though, could also be seen in a relativistic way. Does truth depend on our intellect? St. Thomas’s words are far deeper than this, however. Our intellect is said to be true if its knowledge is in conformity with reality. The intellect is designed to perceive what is real – not only what we feel or wish to be real, but what is authentically real independent of ourselves. The intellect, working through reason, will reject what is unreal and will conform itself to what is real. As St. Thomas says, “knowledge is according as the thing known is in the knower.” (ibid.) The goal of the intellect is to incorporate that which is real into itself and to thus conform itself to reality, and it accordingly has the capacity to reflect a nearly infinite amount of knowledge, to be transformed into the likeness of all things that are real. But for this to occur, there must be a “thing known” as received through the senses, not merely a name assigned to a subjective mental state (the claim of nominalism and many modern philosophers); the intelligibility of being must be based in objective reality itself, rather than a mere figment of our subjective mind.
To understand the dependence of the intellect on objective reality, a comparison can be made with the natural sciences. The “matter” or object of natural science is of course the material, measurable world; by this focus it is limited and yet also refined for a specific task. Similarly, the “matter” of the intellect is being itself, that which is real; natural science, like all other intellectual disciplines, utilizes the intellect to discern what is real or unreal, true or untrue in the material world, but the intellect itself is far broader and can discern reality on both a material and immaterial level. What standards are used by the intellect to know if something is real/true or unreal/untrue? We know that science is ordinarily held to high standards according to the philosophy and experimental method that underly it, but can the same be said for the intellect in general?
The natural sciences, in fact, use and depend upon the same standard principles which are used by the intellect in all its applications. These are called “first principles” and are often studied in the philosophical toolbox called logic. One way science applies these principles is through mathematics, but first principles also go beyond mathematics and enforce other requirements onto the intellect. First principles, unlike scientific findings, are not demonstrable; they cannot be proven by syllogism or experiment. Rather, syllogism and experiment depend upon them to be intelligible. First principles include such self-evident truths (some of the few truths which are truly “self-evident”) as the principle of non-contradiction, that something cannot be true and untrue in the same respect and at the same time. Is there any way to prove this principle? No; it is simply known by all, and its denial leads to pure absurdity and contradicts the very intellect making the denial, preventing the intellect from recognizing reality, while the denial itself is an affirmative truth-statement excluding its opposite and so is self-contradictory.
Imagine if this principle was not followed in the natural sciences. No theory or fact could ever be held definitively; all scientists would have to concede that it could be true or untrue at the same time. This is distinct from admitting human fallibility and ignorance, to humbly say that we believe something is true but could be proven wrong at some point; rather, this denial of non-contradiction would mean that gravity could be real and unreal at the same time, that an organism could be alive and dead at once, etc. The intellect can apply these first principles, which are themselves derived from intuitive knowledge rather than the material world, to discern reality that is immaterial.
How, it may be asked, is reason related to the intellect? Reason can be seen as the primary or most common “application” of the intellect, the means by which it discerns what is true. Human reason, being limited, is called by St. Thomas “discursive” reasoning; reason connects one truth to another, moving from principles to conclusions, and if our conclusions agree with our principles the conclusions are said to be true (ST I, q. 14, a. 7). Reason can then connect conclusions to one another to form concepts, and if these concepts are also judged to be in accordance with our principles, then we consider them to be true as well. The different methods of reasoning, such as deductive, inductive or inferential, all use this fundamental discursive form and depend upon the same logical principles.
Because the intellect is not limited by the “particulars” of experience but rather abstracts the intelligible essences of the things that our senses perceive, coming to an understanding of what a thing truly is, how it is essentially distinct and connected to other things, the intellect itself is immaterial, since its object and method are themselves immaterial. Other animals are incapable of understanding these universal truths because they are limited by their senses to only understand individual things and cannot abstract to know what those things are, how they are related and the higher implications we learn from our experiences. As St. John Paul II wrote, “Within visible creation, man is the only creature who not only is capable of knowing but who knows that he knows, and is therefore interested in the real truth of what he perceives.” (Fides et ratio, 25)
Despite the claim by many people since the time of the Renaissance that reason and faith are either totally separate and should not mix (as many late Scholastics, Islamic thinkers and Protestants believe), that the truths of faith are known purely by God’s infusion of knowledge and cannot be understood more fully by reason, or that faith is fundamentally irrational and only reason can lead to a knowledge of the truth (the standard atheist position), the Catholic Church has always officially held that faith and reason have the same object, namely truth/reality. While the truths of revelation, given by the power of God, cannot be discovered through human reason, they can still be investigated and understood more fully by reason, and can never be incompatible with reason, since our God-given intellect and faith have the same object, namely truth, which cannot contradict itself, and faith is ultimately an uplifting of the intellect by grace to intuit truths which are beyond its natural reasoning. Accordingly, reason is a good that leads to truth and is not only of great use to human life and to faith but is essential to them. To quote St. John Paul II again:
Faith and reason are like two wings on which the human spirit rises to the contemplation of truth; and God has placed in the human heart a desire to know the truth—in a word, to know himself—so that, by knowing and loving God, men and women may also come to the fullness of truth about themselves. (Fides et ratio, opening)
As one proof of this, the Catechism, quoting the First Vatican Council, teaches: “By natural reason man can know God with certainty, on the basis of his works.” (CCC 50) This reflects the teaching of St. Paul, who wrote, “For the invisible things of him, from the creation of the world, are clearly seen, being understood by the things that are made.” (Rom 1:20) While the existence of God can be accepted purely by faith, belief in God is a prerequisite for faith, as is a belief in the particular definition of God, both of which are founded in reason. “For by the greatness of the beauty, and of the creature, the creator of them may be seen, so as to be known thereby.” (Wis 13:5)
Through its power to discern truth, to distinguish reality from unreality, reason can also exorcise the illusions of sin from the world and from ourselves. Using reason, we can determine which interpretations of the world are in harmony with the perfection of God, with the nature of reality as He has created it and with its reflection of the exemplary ideas in his divine mind. Through the power of reason and with the revelation that God is Logos, the Eternal Reason whose Creation is itself fundamentally rational (a truth already perceived to some degree by many Greek and Roman philosophers), we have, as Pope Benedict XVI explained, “demythologized” the world, cleansing it of the superstitions of paganism with its view of reality as essentially arbitrary, capricious and malevolent or amoral:
Thus, insofar as human beings realized that the world came from the Word, they ceased to care about the gods and demons. In addition, the world was freed so that reason might lift itself up to God and so that human beings might approach this God fearlessly.
Further, this same “task” of reason to expunge the errors of unreality must also be applied to the beliefs of Christians. It is one of the greatest points of uniqueness and applicability in the Catholic religion that faith and reason are seen as fundamentally united and harmonious. Almost all other worldviews throughout history have separated and even opposed them to some degree, either as mutually unrelated or with one somehow contaminating or limiting the other. Catholicism, on the other hand, has always officially taught, and has corrected those who erroneously believed otherwise, that faith and reason are both great gifts of God to enable humanity to perceive and conform themselves to being more fully. Accordingly, when faith and reason are separated, not only is reason cut off from truths which it cannot grasp through its own human effort and which can help it to evade errors that stifle reason and lead to immorality, faith is also harmed. Without the light of reason, faith is led astray into the darkness of superstition and subjectivism. As St. John Paul II explained,
Deprived of reason, faith has stressed feeling and experience, and so run the risk of no longer being a universal proposition. It is an illusion to think that faith, tied to weak reasoning, might be more penetrating; on the contrary, faith then runs the grave risk of withering into myth or superstition. (Fides et ratio, 48)
Reason without the enlightenment of faith is similarly led into various errors, both philosophical and scientific, as can be seen from the nominalism of Epicurus, William of Ockham and Immanuel Kant which essentially deny the objective reality and intelligibility of being and thus undermine the necessary foundation of the natural sciences, as well as the more recent views of physicist Stephen Hawking, who proposed that the material world can create itself according to the laws of nature without the need for God. (The Grand Design) The existence of God as Logos is essential for a truly rational philosophical worldview, on which natural science depends for its capacity
to know the disposition of the whole world, and the virtues of the elements, the beginning, and ending, and midst of the times, the alterations of their courses, and the changes of seasons, the revolutions of the year, and the dispositions of the stars, the natures of living creatures, and rage of wild beasts, the force of winds, and reasonings of men, the diversities of plants, and the virtues of roots. (Wis 7:17-20)
Without a God who is Reason and whose Creation is rational and intelligible, both mathematics and science, as well as philosophy itself, lose touch with reality and must assert the validity of reason without any objective basis or standard for verification.
So much for the connection between reason and faith in general. Can this relation be seen more explicitly in Scripture, or is it only a part of the Church’s oral Tradition? While the latter is sufficient in itself, the usefulness and validity of reason is certainly evidenced in Scripture as well. One clear example of this can be seen in Jesus’s modification of the Shema, the most fundamental and revered expression of the faith of Israel. In the Old Testament, this prayer reads: “Hear, O Israel, the Lord our God is one Lord. Thou shalt love the Lord thy God with thy whole heart, and with thy whole soul, and with thy whole strength.” (Dt 6:4-5) In Jesus’s version, however, he makes a key addition: “Thou shalt love the Lord thy God with thy whole heart, and with thy whole soul, and with thy whole mind.” (Mt 22:37) Jesus adds the word “mind”, and in so doing He emphasized that we should also love God and serve Him with our intellects, by studying and learning what is true and using reason to conform ourselves to reality and thus ultimately to its Source. Another passage of Scripture helps to explicate and apply this teaching:
Happy the man who meditates on wisdom and reasons intelligently, who reflects in his heart on her ways and ponders her secrets. He pursues her like a hunter and lies in wait on her paths. He peers through her windows and listens at her doors. He camps near her house and fastens his tent-peg to her walls; he pitches his tent near her and so finds an excellent resting-place; he places his children under her protection and lodges under her boughs; by her he is sheltered from the heat and he dwells in the shade of her glory. (Sir 14:20-27, quoted in Fides et ratio, 16)
St. Paul also teaches another essential benefit of training the mind for right reasoning. In Romans 12:2, the Apostle writes, “And be not conformed to this world; but be reformed in the newness of your mind, that you may prove what is the good, and the acceptable, and the perfect will of God.” Rather than allowing our “understanding” to be “darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their hearts,” (Eph 4:18) we can correct this “ignorance” through meditating on the law of God, studying the truths He has revealed to us both in Creation and in revelation so as to be more fully united with the Divine Logos by living within the light of truth.
The moral teachings given by God through the Church help us on this mission by revealing to us the truth of ourselves and our relations to one another as intended by our Creator; thus, for example, the prohibitions on sexual immorality show that we are meant to give ourselves in the fullness of love with such power that, as in the Holy Trinity, our love can generate new life, and to do so with the total self-giving fidelity and self-sacrifice which is an image of the love for Christ and His Church, in conformity with our God-given human nature and the right use of its faculties. (Eph 5:21-32)
How can we go about accomplishing this great mission that St. Paul has given us, to be “reformed in the newness of your mind” and to live a life in accordance with the will of God? While this instruction is the fundamental purpose of all Catholic moral teaching, reason has a specific and essential role in this pursuit, namely, to moderate the bodily passions. Although we lost the perfect subordination of our bodies to reason through the Fall, it is God’s intention that our intellect should have complete authority over our bodily appetites, as the higher above the lower; the disruption of this order, when we give in to our passions inordinately, without reference to the will of God and the moderation of the intellect, we fall into sin. As St. Ambrose wrote,
That man is rightly called a king who makes his own body an obedient subject and, by governing himself with suitable rigor, refuses to let his passions breed rebellion in his soul, for he exercises a kind of royal power over himself. And because he knows how to rule his own person as king, so too does he sit as its judge. He will not let himself be imprisoned by sin, or thrown headlong into wickedness. (CCC 908)
This honing of the intellect to oversee and discipline our passions in accordance with what we know to be true and good and with our nature is the means by which the virtues can become habituated in us. The life of virtue, perfected by the theological virtues infused by God (faith, hope and charity), teaches us how to avoid sin and makes it easier to do what is good. In this way, we can become more to the likeness of God and so actualize the ultimate purpose of reason by which we are distinguished from irrational creatures, as St. Augustine explains: "Man's excellence consists in the fact that God made him to His own image by giving him an intellectual soul, which raises him above the beasts of the field." (St. Augustine, Gen. ad lit. vi, 12) Scripture lists the natural virtues which we should strive all our lives to foster:
And if a man love justice: her labours have great virtues; for she teacheth temperance, and prudence, and justice, and fortitude, which are such things as men can have nothing more profitable in life. (Wis 8:7)
By taking on human nature in the Incarnation, Christ sanctified not only our bodies but also our intellects, since He possessed both a human body and a human soul. As God, all that Christ took to Himself became ennobled; in His earthly life, Christ demonstrated a humanity purified of all sin and perfected in accordance with the will of God. In His intellect, the use of which is shown throughout His earthly life as He explained His teachings and refuted the erroneous claims of His adversaries in a logical and precise way, as well as by the total discipling of His bodily passions, Christ is fully human, having been in the Incarnation “made in the likeness of men, and in habit found as a man,” (Php 2:7) and yet, through being “tempted in all things like as we are, without sin”, (Heb 4:15) He has shown that reason is truly good.
However, and in conclusion, it is necessary also to state that reason, while given by God, is limited both by human finitude and natural fallibility, and by the corruption of sin by which our “understanding is darkened”. (Eph 4:18) To be able to answer questions which cannot be known by reason alone, such as the true nature of God, His ultimate intention for our lives and the means of our salvation from sin and death, as well as to provide certainty for the foundations of the first principles of knowledge, the intelligibility of Creation and the objective standard of morality, there is a need for the revelation of faith. Without faith, reason is in the end handicapped and will inevitably fall into errors and evils and can never achieve the true unity with God without which we can never find true meaning and happiness in our lives.
 Joseph Ratzinger, In the Beginning… (Grand Rapids, MI: Eerdmans, 1995), 33.
 Ratzinger, In the Beginning…, 5.
One of the major influencers of the modern Evangelical movement, Francis Schaeffer, likely built upon the reason argument of Aquinas. Sorry to introduce such a segue, but Schaeffer was largely responsible for my return to Catholicism in 1972 after a very brief fling with communism. You've captured the essence of Aquinas thinking on this subject. Nice job.
Kaleb, you bring out so many interesting and important points in this reflection on Aquinas and reason/the intellect. In offering further feedback to you, I would only point out that to Aquinas the power of the intellect cannot be satisfied, cannot reach its own potential, short of ultimately desiring to see God, which requires meritorious movements by the person to do good as well as the free gift of Grace bestowed from God. While both elements need to be present for the perfection of human nature, on the purely human level this desire, and this desire alone, fulfills our nature and is both a truth of faith and a truth of reason.
Since we are called to this end in the power of our intellects, grace is an essential requirement for the soul to perform all of its actions in perfect harmony in order to pursue the ultimate end: the natural desire to see God. In the Thomistic sense, therefore, grace is the indispensable means required to see God. In the power of the intellect the desire to see God emanates from our nature itself and our nature is therefore perfected and not destroyed by grace. A good reference here is: ST Q. 110, Art. 4. Once again, excellent job!