Thomas Aquinas, the Angelic Doctor of the thirteenth century, stands as one of the Church’s most profound analysts of human nature. In the Summa Theologica (I, q. 79–83), he teaches that the intellect is ordered to truth and the will to the good. The intellect apprehends reality as it is; the will, enlightened by that truth, freely chooses what is genuinely perfective of the person. When these faculties operate in harmony, man attains his “native fullness”— the flourishing proper to a rational creature made in the image of God. Leo XIII echoes and applies this doctrine with prophetic clarity in Immortale Dei (1885): “If the mind assents to false opinions, and the will chooses and follows after what is wrong, neither can attain its native fullness, but both must fall from their native dignity into an abyss of corruption.”

Aquinas insists that error is not neutral. The intellect, when it assents to falsehood, supplies the will with a defective object. The will, in turn, habituates itself to disordered loves. Virtue becomes difficult, vice easy. Grace can heal, but the natural order itself is wounded. Leo XIII universalizes the insight: a society built on false principles— whether philosophical, political, or moral— will inevitably produce citizens whose minds and wills are malformed. The encyclical was written against the liberal claim that the State may remain indifferent to religious truth. Yet its anthropology is timeless. False opinion and vicious choice are not private matters; they corrode the common good.

Modern society offers a laboratory in which Aquinas’s diagnosis and Leo’s warning are verified daily. Consider first the realm of truth itself. Postmodern relativism, now mainstream in universities and media, denies that the intellect can know objective reality. “My truth” replaces “the truth.” Social media algorithms intensify the damage. Users are fed curated falsehoods that confirm preexisting biases, creating digital echo chambers where assent to error becomes habitual. Conspiracy theories, ideological revisionism of history, and the denial of biological sex are not mere opinions; they are false principles to which millions assent. The intellect, starved of reality, grows flaccid. Aquinas would call this a privation of its proper act.

The will suffers correspondingly. Once the mind no longer sees the good as rooted in being, choice drifts toward pleasure, power, or ideology. The sexual revolution provides the clearest example. When the mind accepts the falsehood that the body is plastic and gender is a social construct, the will is licensed to pursue hormonal mutilation, surgical alteration, and the legal redefinition of marriage and family. What Leo XIII called “an abyss of corruption” is visible in soaring rates of depression, anxiety, and suicide among those who have followed this path. The will, promised liberation, finds only deeper slavery.

Political life mirrors the same pattern. Liberal democracy once assumed a shared moral framework grounded in natural law. Today, that framework has been replaced by procedural neutrality and the supremacy of individual autonomy. Laws that once protected the unborn, the traditional family, and religious liberty are dismantled because the collective mind has assented to the opinion that rights are invented rather than discovered. The will of legislators and voters then “chooses what is wrong”—euthanasia, no-fault divorce, gender ideology in schools— under the banner of compassion. The result is not greater freedom but what Aquinas would term a privation of the common good. Social trust collapses, polarization intensifies, and the state itself becomes an instrument of moral coercion against those who still affirm objective truth.

Education offers another stark comparison. Catholic schools once formed intellect and will according to the ratio studiorum and the studium generale. Contemporary secular education, by contrast, often teaches critical theory before critical thinking. Students learn to deconstruct rather than to know. When the mind is trained to see every hierarchy as oppression and every norm as violence, the will is directed toward perpetual revolution rather than virtue. The “abyss of corruption” appears in graduates who lack both intellectual rigor and moral courage—precisely the opposite of the “native dignity” Aquinas and Leo envisioned.

Even the Church is not immune. Clerical scandals, doctrinal ambiguity on marriage and sexuality, and the quiet acceptance of cultural trends within some parishes demonstrate what happens when shepherds themselves assent to false opinions. The faithful are left confused; their wills, deprived of clear teaching, falter. Leo XIII warned that when rulers and subjects alike reject the light of Christ, “the very foundations of society are shaken.” We see those foundations trembling today.

The inspired teaching of Thomas Aquinas and Leo XIII are not those of despair. Both insist that the remedy lies in the restoration of truth. The intellect must be re-formed by philosophy and theology that respect the order of being. The will must be strengthened by the virtues and the sacraments. Modern society, for all its technological splendor, cannot escape the anthropological laws written into human nature. Attempts to deny those laws produce exactly the corruption the encyclical describes: record loneliness, collapsing birth rates, ideological rage, and spiritual emptiness.

The essay of history is therefore clear. Where minds assent to falsehood— whether the autonomy of the self, the fluidity of truth, or the irrelevance of natural law— the will inevitably chooses what is wrong. Both faculties fall from their native dignity. Only a return to the objective truth of God and the assent of the human will to God’s Will can arrest the descent. In an age that celebrates choice above all, the most radical act may be the humble assent of the mind to what is true and the courageous choice of the will to follow it. Only then can persons and societies reclaim their native fullness of life.

“Do not model your behavior on the contemporary world, but let the renewing of your minds transform you, so that you may discern for yourselves what is the will of God – what is good and acceptable and mature.”  ~Romans 12:2