What sins lead to spiritual blindness?

If the blind lead the blind, both will fall into the pit.

The Pharisees of last Sunday’s Gospel were lost in profound spiritual blindness. Their minds were utterly darkened and they knew not the light of grace, nor even the light of reason – since, reason alone would have at least kept them silent in the presence of the Lord.

Though the one man had been blind from birth, his blindness was only physical. He suffered from blindness of the eyes. The Pharisees, on the other hand, did not receive their blindness at birth; but, instead, gave themselves over to blindness through their obstinacy. Their blindness was spiritual and intellectual. They suffered from blindness of the mind.

If the intellectual blindness which the Pharisees suffered was not contracted at birth, but rather was gained through a later perversion of the light of reason; what lead to this blindness? Whence proceeds blindness of the mind? If only we can discover what actions led the Pharisees into this spiritual blindness, we will be more able to remain ever in the light.

The gift of understanding

In order to understand what blindness of mind is, we must know the virtue to which it is contrary. In fact, spiritual blindness is contrary not simply to a virtue, but to a gift of the Holy Spirit, namely the gift of understanding.

Understanding is that gift by which we are able to penetrate the revealed mysteries and come to an intimate knowledge of the supernatural truths of the faith. Understanding is a supernatural light in the intellect which allows man to grasp the very essence of revealed truths. This gift (like all the gifts) is bestowed on man by God and is a principle within man by which the Holy Spirit moves us to supernatural actions. As with the other gifts, understanding is in all who are in the state of grace; it is necessary for salvation.

Blindness of mind as contrary to understanding

Blindness of mind is the vice opposed to the gift of understanding. More broadly, we may say that it is opposed to the theological virtue of faith – since, understanding corresponds to faith. However, spiritual blindness is specifically opposed to the gift of understanding; since, this blindness denotes the privation of spiritual light and even the hindering of the light of reason.

Blindness of mind (this profound spiritual blindness) indicates not merely a certain weakness of the mind in relation to the consideration of spiritual things, but implies the complete privation of knowledge of supernatural realities. In this way, blindness of mind is more than a mere dulling of the intellect, but goes further to make a man hate and utterly reject spiritual truths. The one who is spiritual blind (like the Pharisees of John 9) cannot in any way begin to understand, apprehend, or penetrate the inner nature of spiritual realities; but, instead, turns away completely from supernatural truth.

On account of blindness of mind, the spiritual light of grace in a man’s soul is lost and the light in him becomes darkness. How great will that darkness be!

What sins lead to blindness of mind?

Certainly, by any mortal sin, the gift of understanding is lost – since, when a man loses charity, he loses also all the gifts of the Holy Spirit. Nevertheless – though there are many mortal sins which cause the lost of understanding and, therefore, lead to spiritual blindness – there is one sin which is directly opposed to understanding and leads immediately to blindness of mind. It is from this sin that we may most accurately say blindness of mind proceeds.

St. Thomas Aquinas tells us that the sins which directly cause spiritual blindness are all mortal sins pertaining to lust. In this matter, the Angelic Doctor follows Pope St. Gregory the Great. But what is it about sins of the flesh, and lust in particular, which causes spiritual blindness?

The mind comes to understand truth through an abstraction from sensible phantasms or images. Thus, the more a man’s mind is freed from those phantasms, the more thoroughly will it be able to consider intelligible realities. On the other hand, the more a man’s intellect is fixed on the sensible realities, the less he will be able to understand the essence of things – since the essence is invisible and immaterial.

The Common Doctor continues: “Now it is evident that pleasure fixes a man’s attention on that which he takes pleasure in. Now carnal vices, namely gluttony and lust, are concerned with pleasures of touch in matters of food and sex; and these are the most impetuous of all pleasures of the body. For this reason these vices cause man’s attention to be firmly fixed on corporeal things, so that in consequence man’s operation in regard to the intelligible things is weakened; more, however, by lust than by gluttony, forasmuch as sexual pleasures are more vehement than those of the table. Wherefore lust gives rise to blindness of mind, which excludes almost entirely the knowledge of spiritual things.” (ST II-II, q.15, a.3)

Thus, it is precisely sexual sin which leads to this spiritual blindness – for lust directs all our attention to the things of earth and makes us blind to the things of heaven. Hence, we may well conclude that the Pharisees probably were struggling with some sort of sexual perversion, some sort of lust – this impurity made them utterly blind to the supernatural realities that were taking place before their eyes.

How to grow in spiritual sight and supernatural understanding

St. Thomas: “Abstinence and chastity, dispose man very much to the perfection of intellectual operation. Hence it is written (Daniel 1:17) that to these children on account of their abstinence and continency, God gave knowledge and understanding in every book, and wisdom.” (ST II-II, q.15, a.3)

We might further point out that St. Thomas himself – who is most famous as the greatest of all theologians and, quite likely, the most brilliant man to have ever lived, excepting the Savior – was gifted with the virtue of chastity. From his youth, when his family attempted to dissuade him from becoming a Dominican by placing a harlot in his room, St. Thomas was inspired by God with the special gift of purity – and he received a cord from the angels as a sign of his virtue. St. Thomas, who was most pure among the saints, was also gifted with the highest understanding. He is called the Angel of the Schools, since angels are entirely pure and the power of their understanding far exceeds the human mind.