Gaius the Platonist was a Greek or Roman philosopher, and a representative of Middle Platonism

Middle Platonism

Middle Platonism is the modern name given to a stage in the development of Plato's philosophy, lasting from about 90 BC, when Antiochus of Ascalon rejected the scepticism of the New Academy, until the development of Neoplatonism under Plotinus in the 3rd century. Middle Platonism absorbed many...

. Very little is known about him except that he was the teacher of Albinus

Albinus (philosopher)

Albinus was a Platonist philosopher, who lived at Smyrna, and was teacher of Galen. A short tract by him, entitled Introduction to Plato's dialogues, has come down to us. From the title of one of the extant manuscripts we learn that Albinus was a pupil of Gaius the Platonist...

, who is known to have published a now lost nine-volume summary of Gaius' lectures on Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

. He taught Platonism

Platonism

Platonism is the philosophy of Plato or the name of other philosophical systems considered closely derived from it. In a narrower sense the term might indicate the doctrine of Platonic realism...

 in the first half of the 2nd century, but almost nothing is known about his philosophical opinions. It has been speculated that the On Plato and His Doctrine written by Apuleius

Apuleius

Apuleius was a Latin prose writer. He was a Berber, from Madaurus . He studied Platonist philosophy in Athens; travelled to Italy, Asia Minor and Egypt; and was an initiate in several cults or mysteries. The most famous incident in his life was when he was accused of using magic to gain the...

 may have been taken from the lectures of Gaius, but this assertion is now seen as dubious. It has also been thought that the anonymous commentary on the Theaetetus

Theaetetus (dialogue)

The Theaetetus is one of Plato's dialogues concerning the nature of knowledge. The framing of the dialogue begins when Euclides tells his friend Terpsion that he had written a book many years ago based on what Socrates had told him of a conversation he'd had with Theaetetus when Theaetetus was...

of Plato, which is partially extant, may have come from his school. Porphyry

Porphyry (philosopher)

Porphyry of Tyre , Porphyrios, AD 234–c. 305) was a Neoplatonic philosopher who was born in Tyre. He edited and published the Enneads, the only collection of the work of his teacher Plotinus. He also wrote many works himself on a wide variety of topics...

 mentions that his works were read in the school of Plotinus

Plotinus

Plotinus was a major philosopher of the ancient world. In his system of theory there are the three principles: the One, the Intellect, and the Soul. His teacher was Ammonius Saccas and he is of the Platonic tradition...

.