The Stoical System

Cleanthes and the other Stoical philosophers had a system of their own.

They:

• rejected the doctrine of the Solid Spheres
• maintained that the celestial regions were filled with a fluid ether, of too yielding a nature to carry along with it, by any motion of its own, bodies so immensely great as the Sun, Moon, and Five Planets.

These, therefore, as well as the Fixed Stars, did not derive their motion from the circumambient body, but had each of them, in itself, and peculiar to itself, a vital principle of motion, which directed it to move with its own peculiar velocity, and its own peculiar direction.

It was by this internal principle, that the Fixed Stars revolved directly from east to west in circles parallel to the Equator, greater or less, according to their distance or nearness to the Poles, and with velocities so proportioned, that each of them finished its diurnal period in the same time, in something less than 23 hours and 56 minutes.

It was, by a principle of the same kind, that the Sun moved westwards, for they allowed of no eastward motion in the heavens, but with less velocity than the Fixed Stars, so as to finish his diurnal period in 24 hours, and, consequently, to fall every day behind them, by a space of the heavens nearly equal to that which he passes over in four minutes; that is, nearly equal to a degree.

This revolution of the Sun, too, was neither directly westwards, nor exactly circular; but after the Summer Solstice, his motion began gradually to incline a little southwards, appearing in his meridian to–day, further south than yesterday; and to–morrow still further south than to–day; and thus continuing every day to describe a spiral line round the Earth, which carried him gradually further and further southwards, till he arrived at the Winter Solstice.

Here, this spiral line began to change its direction, and to bring him gradually, every day, further and further northwards, till it again restored him to the Summer Solstice. In the same manner they accounted for the motion of the Moon, and that of the Five Planets, by supposing that each of them revolved westwards, but with directions, and velocities, that were both different from one another, and continually varying; generally, however, in spherical lines, somewhat inclined to the Equator.

This system seems never to have had the vogue.

The system of Concentric as well as that of Eccentric Spheres gives some sort of reason, both for the constancy and equability of the motion of the Fixed Stars, and for the variety and uncertainty of that of the Planets.

Each of them bestow some sort of coherence upon those apparently disjointed phaenomena. But this other system seems to leave them pretty much as it found them.

Ask a Stoic: Why do all the Stars revolve daily in circles of different diameters parallel to each other and with speeds so proportioned, that they all finish their period at the same time, and preserve the same distance and location with regard to one another?

He can only answer that the peculiar nature or caprice of each Star directs it to move in that peculiar manner.

His system affords him no principle of connection, by which he can join together, in his imagination, so great a number of harmonious revolutions.

But either of the other two systems, by the supposition of the solid firmament, affords this easily. He is equally at a loss to connect together the peculiarities that are observed in the motions of the other heavenly bodies;

the spiral motion of them all; their alternate progression from north to south, and from south to north; the sometimes accelerated, and again retarded motions of the Sun and Moon; the direct retrograde and stationary appearances of the Planets.

All these have, in his system, no bond of union, but remain as loose and incoherent in the fancy, as they at first appeared to the senses, before philosophy had attempted, by giving them a new arrangement, by placing them at different distances, by assigning to each some peculiar but regular principle of motion, to methodize and dispose them into an order that should enable the imagination to pass as smoothly, and with as little embarrassment, along them, as along the most regular, familiar, and coherent appearances of nature.

It maintained its authority, however, without any diminution of reputation, as long as science was at all regarded in the ancient world.

Hipparchus lived almost 300 years before Antoninus.

After the reign of Antoninus and the age of Hipparchus, the earlier philosophers had great reputation in the imaginations of mankind.

To abridge, to explain, and to comment upon them, and thus show themselves, at least, capable of understanding some of their sublime mysteries, became now the only probable road to reputation.

Proclus and Theon wrote tried to invent a new system of astronomy against the System of Ptolemy. But they were regarded as impious to the memory of their so much revered predecessors.