Aquinas on the Blindness of Mind

Seung-Joo Lee
Wednesday, February 2nd 2022

Do you, as a Christian, have to overcome intellectual blindness? To put it more strongly, is it a sin to be blind to truths? On the one hand, it does not seem that intellectual blindness is a sin, for a passage like Exodus 4:11 states that it is God who opens and closes people’s eyes: “Who gave man his mouth? Who makes him deaf or mute? Who gives him sight or makes him blind? Is it not I, the LORD?”

If human’s physical blindness is a result of God’s own act of withdrawal or denial of sight, then isn’t God also the reason for human’s intellectual blindness and, hence, the cause of such eventuation? In John 9:41, moreover, Jesus himself said to pharisees: “If you were blind, you would not be guilty of sin; but now that you claim you can see, your guilt remains.” Even here, did Jesus mean that those who are blind are not guilty of sin, and therefore blindness is not a sin itself?

On the other hand, the Bible clearly condemns spiritual blindness, and this no doubt includes intellectual blindness. 2 Corinthians 4:4–6 is a case in point: “The god of this age has blinded the minds of unbelievers, so that they cannot see the light of the gospel that displays the glory of Christ, who is the image of God. For what we preach is not ourselves, but Jesus Christ as Lord, and ourselves as your servants for Jesus’ sake. For God, who said, ‘Let light shine out of darkness,’ made his light shine in our hearts to give us the light of the knowledge of God’s glory displayed in the face of Christ.”

Aquinas and the Blindness of Mind

Thomas Aquinas treated the problem of intellectual blindness in the Secunda Secundae Partisof his Summa Theologiae and at least four concepts stand out as helpful in dealing with the question at hand. Consequent to defining intellectual blindness as “the privation of the principle of mental or intellectual sight,” Aquinas states that there is an intellectual sight that is provided to humans naturally. It is natural for human beings to know the accidents of things, as well as their essences, and the intellect that enables these perceptions is universally constructed in human nature. Yet, this natural light inherent in any human being may be, for various reasons, “prevented from exercising its proper act,” as there is a possibility of having defective properties in the reason itself either from birth or by later events and thus its activities may be hampered without any volitional intents. This kind of blindness resulting from natural defection, Aquinas argues, is not sin per se,as it “arises from the natural defect of one who cannot see.” So, what makes blindness sinful is an intentional resistance, refusal, or rejection of truths, and this is squarely against the natural order as it involves a deliberate closure of eyes to the principles of things and to the essences of existents.

The second concept that Aquinas uses is the idea that the privation of supernatural principles in the human mind is itself a form of punishment from God. “This privation is blindness,” he argues, “and is a punishment, in so far as the privation of the light of grace is a punishment.” According to Aquinas, the original constitution of human nature is such that supernatural principles and notions were conjoined to nature, but after Adam and Eve’s volitional disobedience, the fallen humanity all suffer from the lack of knowledge in the things heavenly, supernatural, and eschatological. In this context, the intellectual blindness to supernatural truths is both a punishment and a sin, and only by the divine grace can this type of blindness be overcome. The value of theological learning can then be stated as a way to overcome the universal sin of blindness and also as a way to actualize the power of renewed intelligence (or even resurrected intelligence), and both values are not insignificant as theology overcomes the blindness of mind in a way that natural sciences can never do by their own powers and insights.

Thirdly, the light of human mind can be darkened or weakened by vices such as gluttony and lust, as those kinds of sins especially attach people’s souls to corporeal things. “The perfect intellectual operation in man,” Aquinas asserts, “consists in an abstraction from sensible phantasms, wherefore the more a man’s intellect is freed from those phantasms, the more thoroughly will it be able to consider things intelligible, and to set in order all things sensible.” Despite this ideal, the level of attachment that intellect has towards sensible things is sometimes too strong that a soul cannot rise above the corporeal things and grasp the value of spiritual goods; and in this case the mind is blinded by the excessive operations of other powers of nature, such as untamed physical and sexual drives. The solution then is to cultivate virtues. For virtues, such as abstinence and chastity, dispose people to the perfection of intellectual operation, as they not only enable but also encourage people to focus on their intellectual activities and achieve a certain level of “detachment” from the sensual things.

The fourth concept pertains to the idea of intellectual dullness. Aquinas goes on to state that “[d]ull is opposed to sharp: and a thing is said to be sharp because it can pierce; so that a thing is called dull through being obtuse and unable to pierce.” Just as, in the physical sense, the sharpness of one’s eyes are connected to their conjoined ability to penetrate into the details of visible objects, the sharpness of one’s internal eyes, the mind, is precisely connected to the soul’s ability to penetrate into the details of conceivable objects. If your physical eyes possess the highest level of visual acuity, then you would be able to see things in high resolution and, therefore, perceive them more accurately, fully, and deeply. Likewise, the intellectual sharpness is precisely the intellectual acuity that perceives the essence of things more fully, precisely, and deeply, and hence it is a fitting counterpart to human’s intellectual dullness and its ideal alternative. In the light of this, Aquinas argues that intellectual dullness can be a result of vices such as gluttony, for it weakens the reason’s ability to rise above the pleasures of taste; but vices such as lust can blind the mind altogether, for it may exclude the knowledge of spiritual principles completely from the mind, heart, and soul.


Thus, in conclusion, Aquinas provides a number of categories that can still help us think more sharply about what counts as intellectual blindness, and the causes and solutions of such eventuation. In order to overcome the blindness of mind with respect to heavenly things, then, what we ultimately need is divine grace, supernatural theology, and godly virtues, and without such gifts it is certain that no one will ever see the Lord (Heb. 12:14). Furthermore, it has to be noted that supernatural grace, knowledge, and virtues are not provided abstractly and accidentally by the things of this world, but concretely in the Lord Jesus Christ, as he taught so profoundly, in John 8:12: “I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life.”

Dr. Seung-Joo Lee (PhD, Vrije Universiteit Amsterdam) is Academic Support Officer at Reformed Theological College in Melbourne, Australia, and Elder at Knox Presbyterian Church of Eastern Australia.

Wednesday, February 2nd 2022

“Modern Reformation has championed confessional Reformation theology in an anti-confessional and anti-theological age.”

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