Thomas von Aquin: Der Theologe, der die Sterne mit der Seele versöhnte

Faith Meets the Cosmos

In the intellectual world of the 13th century, few thinkers shaped Western thought more deeply than Thomas von Aquin (1225–1274 CE).
A philosopher, theologian, and Dominican friar, Aquinas sought to reconcile the wisdom of Aristotle with the revelations of Christian theology.
In doing so, he gave astrology—then a thriving science inherited from Greek, Arabic, and scholastic traditions—a carefully reasoned place within Christian philosophy.

While Aquinas did not practice astrology, he understood its logic and influence. His writings reveal both a deep respect for cosmic order Und a firm defense of human freedom, producing the famous dictum:

“The stars incline; they do not compel.”

This single phrase would define the Church’s attitude toward astrology for centuries to come.

The Medieval Context: A World of Harmonies

By the time Aquinas was writing, astrology had already entered the university curriculum.
Texts by Ptolemaios, Abu Ma‘shar (Albumasar), Und Al-Kindi had been translated into Latin, blending Aristotelian natural philosophy with celestial mechanics.
Astrology was taught alongside medicine and geometry, considered part of understanding God’s creation through natural causes.

For scholastics like Aquinas, the universe was not divided between spirit and matter—it was a hierarchy of causation. The celestial spheres transmitted the divine will through orderly motion; the sublunar world received and expressed these influences in the forms of weather, temperament, and time.

The question Aquinas faced was not whether the heavens acted upon the earth—that much was clear to all natural philosophers—but how far their influence reached into human choice and salvation.

The Summa Theologica: Astrology and Natural Causes

In his Summa Theologica (Part I, Question 115), Aquinas addressed the issue directly: “Whether heavenly bodies are the cause of human acts?”
He acknowledged that celestial movements influence physical bodies—for example, tides, weather, and even the balance of humors in the human constitution.
However, he drew a crucial distinction between the body, which is subject to nature, and the soul, which possesses reason and free will.

According to Aquinas:

• The stars can affect bodily dispositions, such as health or emotional temperament.

• They cannot compel the rational soul, which is directed by intellect and will.

• Therefore, astrology may reveal tendencies, but not necessities.

In this synthesis, Aquinas preserved the scientific integrity of astrology while safeguarding moral responsibility.
He neither condemned the art nor accepted it uncritically; rather, he placed it within the framework of divine providence—a lawful, ordered cosmos in which human freedom still participates.

The Stars as Instruments of Providence

For Aquinas, the stars were not gods or independent powers, as the pagans believed. They were sekundäre Ursachen—instruments of God’s primary will.
Er schrieb:

“Heavenly bodies are moved by spiritual substances and act as instruments of the divine will.”

Thus, astrology was part of natural theology: the study of how divine wisdom manifests in the material world.
The stars revealed the harmony of creation but could never overrule the Creator’s grace.

This vision unified faith and science in a single hierarchy of meaning:

• God — the First Cause and ultimate source of order.

• Angels and intelligences — movers of the spheres.

• Celestial bodies — transmitters of natural influence.

• Humans — beings of reason, able to know and transcend nature.

The Influence of Arabic Astrology

Aquinas’s nuanced position was shaped by the Arabic philosophers whose works dominated medieval universities: Al-Kindi, Avicenna, Und Abu Ma'shar.
From them, he inherited the idea of celestial causality operating through heat, light, and motion—natural rather than magical forces.

But where Al-Kindi and Abu Ma‘shar saw astrology as a rational science within the chain of causes, Aquinas added a theological correction:

• Nature operates through cause and effect.

• Yet grace operates beyond nature.
  Thus, the astrologer could read the tendencies of time, but the soul remained free in its moral and spiritual choices.

Legacy and Enduring Influence

Aquinas’s synthesis became the official philosophical position of the Catholic Church.
It allowed astrology to be studied as part of natural philosophy, as long as it did not claim power over the soul or divine will.
This balanced view kept astrology intellectually alive through the Renaissance, where thinkers like Marsilio Ficino Und Giovanni Pico della Mirandola debated its moral and spiritual meaning.

In Ficino’s Three Books on Life, the echoes of Aquinas are clear: the heavens influence our temperament and vitality, but wisdom allows us to cooperate consciously with the stars, not submit to them.

The Theologian of Cosmic Freedom

Thomas Aquinas gave astrology its moral center.
He reminded both theologians and astrologers that knowledge of the heavens is not an end in itself, but a way to understand the order of creation.
In his vision, the stars express divine reason, but the human soul mirrors divine freedom.

In that balance—between law and grace, cause and choice—Aquinas offered a vision of the cosmos that remains profound today:
a universe where destiny and conscience coexist,
and where studying the heavens is an act of reverence, not rebellion.