Heraclides descended from a wealthy family from Heraclea Pontica. He was a philosopher and astronomer, the first to propose a mixed geo-heliocentric system of the universe. His vast bibliography, which unfortunately does not survive today, spanned the fields of physics, astronomy, metaphysics and meteorology.
He studied in the Academy of Athens where he became one of Plato’s students and later a student of Aristotle in the Lyceum. In the Academy he befriended Speusippus, the successor of the school. Upon Speusippus’ death, Heraclides was one of the candidates for headmaster of the Academy, but lost to Xenocrates. He returned to his hometown Heraclea where he founded his own philosophic school. Heraclides possessed profound knowledge on Pythagorean philosophy and was a proponent of Demorcitus’ theory of the atom.
Heraclides was active primarily in astronomy. He proposed the mixed helio-geocentric model of the cosmos according to which the sun, the moon and the planets of the solar system rotate around the Earth, except from Venus and Mercury, who orbit the Sun. Heraclides also postulated that the Earth completes a rotation around its axis in 24 hours. He was the first philosopher to hold such a belief. This model proposed by the philosopher is believed to have served as the basis for the astronomical model of Tycho Brahe.
Heraclides was a prolific writer. Like most of his contemporaries, he wrote a book On Nature, a treatise on physics. Furthermore, he wrote the philosophical books On the Pythagoreans, On Hades and on Uranus, On Findings and Zoroaster, books on the philosophy of physics, literary critiques, books on mysticism and books on theurgy or medicine. As a Platonic philosopher, Heraclides endorsed the concept of the immortality of the soul as well as reincarnation. According to him, the soul is made of light (φῶς) and aether (αἰθέρα). It originates from the Galaxy.
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