Astrology Definition: What Astrology Is, Its History, and How It Works

What Is Astrology?

Astrology is a symbolic system that studies the relationships between the movements of celestial bodies and events, qualities, and patterns on Earth. It is one of the oldest organized systems of knowledge in human history, predating modern astronomy, psychology, and most of the world's major religious traditions.

The word "astrology" comes from the Greek astron (star) and logos (word, reason, or study). Literally: the reason of the stars, or the language through which the stars are read. This etymology points to astrology's fundamental claim: that the heavens speak, and that this language can be learned.

At its most basic level, astrology proceeds from a single premise: what happens in the sky corresponds to what happens on Earth. This correspondence principle, codified in the Hermetic axiom "as above, so below," does not necessarily claim causation. The planets do not force events or determine personalities. Instead, astrology describes a pattern: the state of the cosmos at a given moment is mirrored in the state of things on Earth at that same moment. The chart is a map, not a cause.

A Brief History of Astrology

The shift to horoscopic astrology (the casting of birth charts for individuals) first appeared in Hellenistic Egypt around 200 BCE. This was a profound intellectual development: the idea that the configuration of the sky at the precise moment of an individual's birth could map that person's character and life trajectory. This development required both the Babylonian celestial data and the Greek philosophical tradition of the individual soul.

The system was codified by Claudius Ptolemy (c. 100-178 CE) in his Tetrabiblos, which became the canonical text of Western astrology for over a thousand years. Ptolemy established the tropical zodiac, the planetary rulerships, the house system, and the theory of aspects that still form the foundation of Western astrological practice.

Astrology flourished throughout the Islamic Golden Age (8th-13th centuries CE), where Arab scholars preserved and expanded the Hellenistic heritage, translating Greek texts and adding their own advances in astronomical precision. It then flowed back into Renaissance Europe, where it was considered a legitimate scholarly discipline and was taught at major universities alongside medicine and theology.

The decisive split between astrology and astronomy occurred in the 17th century with the Scientific Revolution. As Copernicus, Galileo, and Kepler (himself a practicing astrologer) replaced the geocentric model with the heliocentric one, astrology lost its cosmological foundation in academic science. By 1700, astrology had largely retreated from universities into popular almanac culture.

The 19th century saw astrology revived by the Western esoteric tradition, particularly through the work of the Hermetic Order of the Golden Dawn, which integrated astrology with Kabbalah, tarot, and ceremonial magic. The 20th century saw a major modernization through the work of figures like Dane Rudhyar, who reframed astrology as a psychological and humanistic discipline rather than a predictive one, drawing on Carl Jung's depth psychology.

How Western Astrology Works

Western astrology uses four primary components to describe any given moment in time:

A complete astrological interpretation weaves these four layers together. A sentence of analysis might read: "Mars (planet of action and desire) in Scorpio (intense, penetrating, meaningful) in the 8th house (shared resources, transformation, the unconscious) squaring (tension) Pluto (power, transformation, the depths) in the 5th house (creativity, love affairs) describes a person whose creative and romantic life is characterized by intense, meaningful power dynamics and a drive to penetrate beneath the surface of experience."

For a detailed breakdown of how to read a birth chart, see our complete guide to the astrology chart. For the individual signs, see the zodiac sign dates guide.

The Main Branches of Astrology

• Natal astrology: The study of birth charts. This is what most people mean when they say "astrology." A natal chart maps the sky at the moment of birth and describes personality, potentials, and life patterns.
• Mundane astrology: The study of events affecting nations, cultures, and collective humanity. Uses charts for nations, cities, and historical events.
• Predictive/transit astrology: The study of how current planetary movements interact with a natal chart to identify timing and themes in a person's life.
• Electional astrology: Choosing the optimal time to begin a project or take action, based on favorable planetary alignments.
• Horary astrology: Answering a specific question by casting a chart for the moment the question is asked.
• Medical astrology: The oldest practical application, correlating planetary influences with health and healing.

Western vs Vedic Astrology

Two major astrological traditions exist today: Western (Hellenistic/tropical) and Vedic (Jyotish/sidereal).

Astrology and Science

Astrology is not a science in the modern sense. Controlled studies have generally not supported the specific claims of astrological prediction, and there is no known physical mechanism by which planetary positions could influence human personality at birth.

However, dismissing astrology on purely scientific grounds misunderstands what astrology is. As a symbolic system rather than a mechanistic causal theory, astrology operates more like a language than a physics experiment. The question of whether it "works" is less meaningful than the question of whether its practitioners find it illuminating and practically useful, which many do, including figures as significant as Carl Jung, W.B. Yeats, and Johannes Kepler.

Jung's concept of synchronicity, the meaningful correlation of inner and outer events without a causal link, provides the most philosophically coherent framework for understanding why astrology might be useful without being scientifically provable. The birth chart does not cause your personality. It maps, symbolically and synchronistically, a moment in the cosmos that corresponds to your nature.

Astrology in the Esoteric Tradition

What Astrology Is Used For

• Self-understanding: The natal chart as a personality map, revealing strengths, challenges, and the themes most central to this life.
• Timing: Understanding when certain energies are active or blocked, using transits and progressions to navigate timing decisions.
• Relationship understanding: Comparing two charts (synastry) to understand the dynamics, challenges, and gifts of a relationship.
• Psychological depth work: Many therapists and depth psychologists use astrological insight as a supplementary lens for understanding a client's patterns.
• Spiritual practice: Working with lunar cycles, planetary hours, and the seasonal rhythms of the zodiac as a framework for contemplative and ceremonial practice.