The fundamental difference between ancient and modern science is not at all in the field of theory. Sir William Thomson was just as metaphysical as Pythagoras or Raymond Lully, and Lucretius quite as materialistic as Ernst Haeckel or Buchner.
But we have devised means of accurate measurement which they had not, and in consequence of this our methods of classification are more quantitative than qualitative. The result has been to make much of their science unintelligible; we no longer know exactly what they meant by the four elements, or by the three active principles, sulphur, mercury, and salt. Some tradition has been preserved by societies of wise men, who, because of the persecutions, when to possess any other book than a missal might be construed as heresy, concealed themselves and whispered the old teaching one to another.
The nineteenth century saw the overthrow of most of the old ecclesiastical tyranny, and in the beginning of the twentieth it was found once more possible to make public the knowledge. The wise men gathered together, discovered a student who was trustworthy and possessed of the requisite literary ability; and by him the old knowledge was revised and made secure; it was finally published in a sort of periodical encyclopedia (already almost impossible to find, such was the demand for it) entitled The Equinox.
Now in the science of antiquity, much classification depended upon the planets. Those things which were hot and fiery in their nature, lions, and pepper, and fevers, were classed under the Sun or Jupiter or Mars; things swift and subtle under Mercury; things cold and heavy under Saturn, and so forth.
Yet the principles of most of the planets appeared in varying proportions in almost everything; and the more equally these proportions were balanced and combined, the more complete was anything supposed to be, the nearer modelled on the divine perfection. Man himself was called a microcosm, a little universe, an image of the Creator. In him all the planets and elements had course, and even the Signs of the Zodiac were represented in his nature. The energy of the ram was in his head; the bull gave the laborious endurance to his shoulders; the lion represented the courage of his heart, and the fire of his temper; his knees, which help him to spring, are under the goat -- all works in, and is divided and subdivided in, beauty and harmony."
Aleister Crowley, Moonchild
(LIBER LXXXI - The butterfly net)