Galileo

But Galileo’s scientific impact was not limited to his brilliant calculations in the realm of astronomy or to his formulations of the laws of accelerations and dynamics. Of equally far reaching influence upon the development of modern philosophy and science were the assumptions and methods he employed in the study of nature in general. Democritus, as early as the fifth century B.C.E., reduced all things in the universe to atoms in motion, in short, to matter. Later, Lucretius (89-55 B.C.E.) showed how deceptive appearances can be; he described how a person standing on one side of a valley might see on the other side something that looked like a white cloud only to find upon going there that the “cloud” was a flock of sheep. Similarly, Galileo stressed the distinction between appearance and reality, where appearance is made up of secondary qualities while reality consists of primary qualities. We cannot trust appearances as a reliable path to truth. For example, our notion based upon appearances leads us to the erroneous conclusion that the sun moves around the earth. Or, a tree or a rock appears to be a single solid thing but in reality is composed of a multitude of atoms. The most accurate knowledge available to us is produced by the mathematical analysis of moving bodies, not only as in astronomy but also in physics.

The rigor of Galileo’s thinking lay in his method of focusing strictly upon exact mathematical demonstrations and avoiding second hand information based simply upon tradition and opposing conjectures contained in books. “To demonstrate to my opponents the truth of my conclusions,” Galileo said, “I have been forced to prove them by a variety of experiments.” Having in mind the distinction between primary and secondary qualities, Galileo certainly gave the impression that only those qualities that belonged to bodies or matter have true reality. Primary qualities, such as size, position, motion, and density, are truly real because they can be dealt with mathematically. By contrast, secondary qualities, such as color, taste, emotions, and sounds, “reside only in consciousness; if the living creature was removed, all these qualities would be wiped away and annihilated.” A human being can be defined as a body with physical organs. But when one is defined as a person, it turns out that most personal characteristics are represented by secondary qualities. This would mean that either these secondary qualities must be explained mathematically as being aspects of the primary qualities of matter or that the secondary qualities do not participate at all in the realm of reality. In either case, their unique dignity, value, or special status of human beings in the nature of things is severely diminished.