Plato's Doctrine Respecting the Rotation of the Earth and Aristotle's Comment Upon That Doctrine — A Closer Reading

The Disputed Passage and Its Interpreters

Grote begins by quoting the Greek text of Timaeus 40B as it appears in Stallbaum's edition: 'Γῆν δὲ τροφὸν μὲν ἡμετέραν, εἱλλομένην δὲ περὶ τὸν διὰ παντὸς πόλον τεταμένον...' He notes that the obscurity of this passage is 'amply attested by the numerous differences of opinion.' Ancient readers, including Aristotle, understood it as asserting the Earth's rotation, while Cicero mentions that some believed Plato indicated the same doctrine 'obscurely.' Plutarch devoted a critical chapter to the question. Grote also references a Doric treatise often published with Plato's works, which he treats as a later interpretation rather than a genuine source.

The Cosmical Axis as a Solid Revolving Cylinder

Grote's central claim is that Plato conceived the cosmical axis as a 'solid revolving cylinder.' He draws on M. Cousin's own admission that the axis moves, and on the synonyms offered by commentators—such as sphingomenēn (bound) and peridedemenēn (tied around)—to argue that these words actually prove the Earth rotates with the axis. Grote writes: 'The word εἱλομένην or ἰλλομένην has no distinct meaning at all, if it does not mean this.' He rejects the objection that such a view would involve Plato in astronomical inconsistency, insisting that the plain meaning of the text must be accepted.

The Earth's Function as Regulator of the Axis

Grote explains that the Earth's rotation is not intended to explain astronomical appearances; it is a consequence of its position. The Earth is 'packed or fastened round the centre of the cosmical axis,' and thereby participates in the axis's movements. Its function is to 'uphold and regulate the revolutions of the cosmical axis,' ensuring uniform and constant motion. This role, Grote argues, is why Plato calls the Earth the 'first and oldest of intra-kosmic deities.' The movement of the Earth is 'only an incidental consequence' of its necessary position for performing this regulatory function.

Contrast with Later Astronomical Developments

Grote distinguishes Plato's conception from later astronomy, noting that the Earth's rotation in the Timaeus is not a rotation on its own axis but a participation in the axis's movement. He contrasts this with the modern idea 'que la terre tourne sur elle-même.' The essay thus illustrates the 'scientific character of the Platonic and Aristotelian age' before the subsequent development of astronomy. Grote's analysis is firmly grounded in the text and in the responses of ancient and modern commentators, avoiding anachronistic judgments.

Grote's dissertation is best read as a focused philological and philosophical argument, not as a general introduction to Plato's cosmology. Readers should attend to his step-by-step rebuttal of M. Cousin's five arguments, and to his insistence on the literal meaning of the Greek verb. The essay rewards those who are willing to engage with the original passage and the scholarly debate it has generated. Grote's own position is clear: the Earth rotates because it is bound to the revolving axis, and this is what Plato intended.