Galileo and the Scientific Revolution #1: Introduction

The most important shift in Western thought came into its own with the Enlightenment, beginning in the 17th century. It is this context that the modern social sciences were born. It was not the case that human beings began asking questions about themselves for the first time. Women and men have always done so. The shift came when the place of God in the asking of the questions changed. Previously, most thinkers would not have considered answering anthropological questions without some basic theological assumptions. The thinkers of the Enlightenment began pushing the theological assumptions further and further into the background until, for many, the need for God to answer the human questions all but disappeared.

Before the Enlightenment there was a common view of the world based upon assumptions that had been held for centuries. That this view is different from the view of the world today is displayed in the difficulty modern people have in, not only accepting their view of the world, but understanding how they could have believed it themselves. Of course, we should not forget that 400 years from now people may think the same thing about us.

This common view finds its foundations in the cosmology of the time, which was a mixture of biblical thought, Aristotelianism, and Ptolemaic thought. In this cosmology, the earth was believed to be the center of the cosmos and it was also believed that the earth was not only the center of the universe, but it was at the center of a series of concentric spheres. These spheres, which numbered at least 53, were believed to carry the stars and the planets and accounted for their motion. This theory was the result of the conviction that there could be no empty space in connection with the prevailing views of motion.

The understanding of motion that under girded Aristotle's cosmology held that motion would continue as long as the cause of the motion was in contact with the object it was moving. With this assumption in place, the logical question would be how the planets moved in the sky without falling to earth. This was accounted for by positing, not that they were free moving bodies, but that they were contained within the spheres. It was also believed that the heavenly bodies were made of a special "higher" element. They were better, therefore, in the hierarchy of being. This accounts for why pre-Enlightenment astronomers believed the planets traveled in circular paths and that the spheres were round. The circle and sphere were believed to be perfect movements. They were perfect creations of a perfect God; and all movements were directly from the divine. It is not difficult in this cosmology to understand that God is needed to explain it.

The ancient astronomers were not unaware of the difficulties with this interpretation. For example, many had observed that the planets did not travel in perfect circular orbits. In response, many offered modifications of the Aristotelian cosmology. Claudius Ptolemy has the distinction of solving the problem. He proposed that the change in speed and direction of planets was the result of cycles and epicycles. While it was true, said Ptolemy, that the planets and stars moved around the earth in circular paths, they were not simple circular paths. A planet moved around the earth in circular motion, but is was also moving through a series of smaller circular orbits. It was this continual series of orbits that moved on the larger circular path around the earth. In this theory, the perfection of the cosmos as demonstrated in circles and spheres was maintained.

Theologically, it was believed that the earth, particularly human beings upon it, was the center of God's creation, and that God's creation was perfect on account of its geometric design. While the Bible did not specifically teach that the earth was the center of creation or that circles and spheres were perfect, it seemed correct that such would be the case. Genesis seemed to indicate that the creation drama was brought about by God for the salvation of humanity. Why would anyone assume that the earth was not the center of creation?

The main point to be gleaned is that the accepted cosmology before the Enlightenment was based on long held and cherished assumptions. To change those assumptions would cause a cultural explosion. Galileo Galilei was the one who struck the match.