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  • 2/21/2004

Galileo Galilei

( 2/15/1564- 1/8/1642)

Born in Pisa in 1564, Galileo Galilei, known usually as just Galileo, taught first in his native city, and then in Padua. FromPadua he went to Florence, called there by Cosimo II, who nominated him head mathematician and philosopher. In 1616 the Roman Inquisition, summoning Galileo for interrogation, condemned the Copernican heliocentric system and prohibited Galileo from teaching it. In 1623 Galileo, in controversy with the Jesuit Orazio Grassi, publishedIl Saggiatore (The Appraiser), and in 1632,Dialogue on the Two Greatest Systems of the World. This persistent defense of the heliocentric system was the cause of Galileo's second trial and of his condemnation in 1633. He passed the last years of his life in the village of Arcetri near Florence, where he died in 1642. (More than 350 years later the Catholic Church formally apologized for its treatment of Galileo.)

General Doctrine

Galileo is one of the most representative figures of the Renaissance. An excellent writer, he made discoveries in the entire field of physics, especially in the science of mechanics, in astronomy and in the methodology of science. Nevertheless, he is not a philosopher in the strict sense of the word.

Notable is his method for scientific research, which enabled him and his disciples to achieve great discoveries. His theory of knowledge, however, is not sustained by an adequate metaphysics; the metaphysics which logically should support his theory is atomistic, and does not conform to the principles of the Catholic faith, which Galileo sincerely professed.

The Galilean Method

The theory of knowledge of Galileo begins, like that of Aristotle and Thomas Aquinas, with experience. But Aristotle and Aquinas use experience in order to arrive at the absolute values of matter and form, while Galileo is content to remain in the field of experience. His purpose is to tell us notwhat nature is, but how nature reveals itself. He studies nature to learn the laws which govern natural phenomena, and not as steppingstone to reach an understanding of the underlying reality of things.

Nature, according to Galileo, has a mathematical structure; its characteristics are triangles, rectangles, circles, spheres, cones, pyramids, and other mathematical figures. Mathematics represents the rational element of nature, and when the full content of mathematics is finally discovered, then nature is apprehended.

To arrive at the knowledge of such mathematical laws, Galileo says, we must make use of sense and reason, by passing through three stages:

1. The observation of the facts which fall within our experience;

2. The elaboration of a mathematical hypothesis as a presumed explanation of the phenomena under observation;

3. Verification of the hypothesis through new facts of experience. If the verification of experience agrees, the hypothesis becomes law.

This method of Galileo without doubt led to numerous scientific discoveries. But it is to be noted that in following this method we are in the field of science and not philosophy; we learn that phenomena appear according to mathematical formulae, but we learn nothing of the reality from which these phenomena originate. Such a method falls short of being a true metaphysics.

If it is necessary to suppose a metaphysical basis for such a method, the only one that can be attributed to it is materialistic atomism, according to which the ultimate or basic elements are quantity (atoms) and motion. If for Democritus (an early Greek naturalistic philosopher) the atoms moving in space were directed by chance, for Galileo they are directed by mathematical laws. Indeed, beginning with Galileo, this new physio-mathematics was to take the place of traditional metaphysics.

Furthermore, it must be kept in mind thatqualitative values find no place in physical mathematics for the simple reason that they (e.g., odors, tastes, etc.) are not reducible to mathematical formulae. Hence it becomes necessary to distinguish between quantitative elements (expansion, weight, motion) and qualitative elements (odors, tastes, etc.). The first are called objective, having a reality distinct from the subject; the second will be called subjective, being modifications of the subject and devoid of any objective reality.

This theory, proposed by Galileo and afterwards followed by John Locke in his noted distinction between primary and secondary qualities, was to become part of modern thought. Now, such mechanism is in opposition to the transcendence of God and hence in opposition to the very faith professed by Galileo. Consequently, the Galilean method must be considered as a method of science and not as a theory of knowledge, for knowledge is based on metaphysics.

The Trial of Galileo

It is necessary to hold fast to this distinction between science and philosophy (theology) in order to find the reason for the two condemnations (1616 and 1633) the Catholic Church's Holy Office (Inquisitors) made of Galileo's defense of the heliocentric system of Copernicus.

Nicolaus Copernicus, in his famousDe revolutionibus orbium caelestium (Concerning the Revolutions of the Heavenly Spheres), had proposed, without giving direct proofs, a new astronomical system which can be summarized in this way: The world is spherical and finite, its extreme limits being the heaven of the fixed stars. Heavenly bodies are all spherical, and their movement is circular and uniform. The sun is located at the center of the system, and the planets rotate around it. The earth is a planet and has a double movement, revolving daily around its own axis, and annually around the sun.

Galileo was the announcer of this system. He too neglected to give direct proofs; he had the intuition of genius rather than scientific knowledge. In reference to the two trials to which Galileo was subjected for teaching this radical system, it is necessary to remember the good faith on both sides of the dispute: Galileo, a convinced Catholic, and the members of the Commission of the Holy Office, among whom were persons like Robert Cardinal Bellarmine, far above any personal intrigue.

Moreover, there were failings on both sides. Galileo did not confine himself to proposing the heliocentric doctrine as a scientific hypothesis; but to corroborate it he became an interpreter of the celebrated Scriptural passage which speaks of Josue's causing the sun to stand still. The members of the Commission of the Holy Office, according to the prejudice then in vogue, believed that the destruction of Aristotle's physics meant the ruin of his metaphysics as well, and that the whole body of medieval thought would crumble. Certainly, they were not disposed to accept the new system.

If there had been a consciousness of the limits of science and philosophy -- a recognition that the one is the knowledge ofhow and the other of thewhy of nature; if it had been considered that physical science is non-philosophical and has nothing to do with the principles of metaphysics, and that the principles of metaphysics do not reveal the laws that regulate nature, it would have been possible to avoid all that happened. But the times were not yet ripe for such a distinction between science and philosophy, and history is obliged to record the unhappy results.

Direct proofs of the Copernican system were formulated only later, with Johannes Kepler (1571-1630), who established the three famous laws which regulate the movement of the stars; and withNewton (1642-1727), who completed the system with the law of universal gravitation, thus explaining the equilibrium of heavenly bodies.

It should be noted that in 1993 the Catholic Church recognized its error regarding Galileo and apologized for his condemnation by the Commissioners of the Holy Office at that time.

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