SECOND YEAR--FIRST SEMESTER                                Galileo                    Lecture 4                                                                David Banach


Galileo and the Origins of the Modern World

For the eye altering alters all;/The senses roll themselves in fear,/And the flat earth becomes a ball.  (William Blake)

Mathematics is the language with which God has written the universe.    (Galileo)


   I. Galileo and Modernity: The Modern world is the result of the transformation effected by the integration of the scientific method and the scientific world view into human life and culture. Galileo, more than any other single figure, is responsible for the form that this new method and world view took.  The transformation of human life by the technology made possible by science is obvious, but the effects of two central ideas that crystallized in the thought of Galileo are equally important.

A.      Scientific Method as a model for Reason: The new method of knowledge introduced by Galileo and the Scientific Revolution increased the confidence in the power of human reason and its ability to transform civilization. The hundred or so years following the Scientific Revolution (the 1700’s, the Enlightenment) saw an unprecedented revision of the forms of human government and culture on the basis of the application of this new method. The Post-Modern world will ask whether Science can deliver on the promise of objectivity and whether a society can be ordered on the basis of reason.

B.       The Mechanistic world view: The Scientific revolution introduced a radically new view of the world as a mechanism composed of inert parts, whose configuration and mechanical relations determine all of its properties. Deism was the view that God was merely the caretaker of this grand mechanism. Having set it in motion, he stands back and watches it run with the mathematical precision of a machine. The Post-Modern world will ask whether human values and the human soul can find a place in this mechanistic world. This is the real conflict between science and religion.


When Galileo caused balls, the weights of which he had himself previously determined, to roll down an inclined plane; . . .a light broke upon all students of nature. They learned that reason has insight only into that which it produces after a plan of its own, and that it must not allow itself to be kept, as it were, in nature's leading-strings, but must itself force . . .nature to give answer to  questions of reason's own determining.                                                          Immanuel Kant,  Critique of Pure Reason


 II. Galileo and The New Scientific Method: Purifying the Appearances. The essence of the method introduced by Galileo was a purification of the appearances to separate the relative from the absolute.

A. The Copernican Hypothesis and the motion of the sun: The senses tell us that the sun is moving. Using our minds we can see that the motion of the sun in the sky is really our motion, merely relative to us.

B. Terrestrial motion and the method of experiment or trial:

        1. Free fall: Aristotle believed heavy objects fell faster than light objects, since they had more earth than air or fire or water in them. Galileo saw that all objects fall at the same rate. The senses supported Aristotle. Galileo’s experiments aimed at purifying the senses and isolating only the effects of weight from all the other causes involved such as air resistance, friction, and buoyancy.

        2. Inertia: Aristotle thought that an object in natural motion moved to its natural place and stopped and that to keep it moving in violent motion required energy. Galileo formulated the law of inertia: that an object in motion tends to stay in motion. The senses supported Aristotle. Only Galileo’s purification of the senses in experiments proved him to be correct.

                C. Mathematical analysis of motion  ( Discourse on Two New Sciences, 1638)  

1. Galileo discovered that the rate of acceleration of fall followed a mathematical law. The distance traveled on the inclined plane was proportional to the square of the time.

2. Galileo discovered that all projectile motion followed a parabolic path. The horizontal motions and the vertical motions of a moving object could be separated and described by a simple set of mathematical equations or laws.

D. Three Famous Experiments: Galileo perfected the method of experimenting by controlling the variables to isolate one pure form as it exists purely or absolutely, independent of us and of other causal influences.

        1. The Pendulum: Used to demonstrate the law of inertia and that heavy and light bodies fall at the same rate. Galileo also discovered the mathematical laws governing the length of the string, the period of the motion, and the amplitude of the swing.
2. The Inclined Plane and the Rate of Acceleration: Galileo used the inclined plane to slow the motion of falling objects enough to accurately measure how their speed increased.

        3. Projectile Motion: Galileo also used the inclined plane to control the speeds and heights of projectiles in order to discover the mathematical properties of their paths.

E. Two kinds of properties: The application of the new method of separating the relative from the absolute to sensible qualities produced a transformation of world view.

1. Primary properties are the properties really in the object such as the size, shape, number, or speed of  the atoms or particles of matter.

2. Secondary properties are the effects that the object has on us and exist only in us,  not in the object itself. (E.g. the tickle of the feather.) Galileo saw that all sensible qualities such as color, sound, warmth, taste, and smell were really only in the mind.



Do not all charms fly/ At the mere touch of cold philosophy?/ There was an awful rainbow once in heaven:
We know her woof, her texture; she is given/ In the dull catalogue of common things./ Philosophy will clip an Angel’s wings,
Conquer all mysteries by rule and line,/ Empty the haunted air, and gnomed mine –/ Unweave a rainbow…     (John Keats)


May God us keep/ From single vision, and Newton's sleep!     (William Blake)


 III. Galileo and The New Scientific World View.

 A. Aristotelian Scholasticism. (The Medieval view, which Galileo criticizes) The basic idea of the view that dominated the late middle ages was that all objects have an internal nature (essential form, species) that determines what the thing is. The job of science was to understand this nature and its relations to other natures. This view had three basic features:

1. Natures are occult or hidden. They are more than just the observable qualities that one can perceive with the senses. Just as our nature, our soul, is more than our body and its qualities, a squirrel is more than just the set of qualities we can perceive (its furriness, shape, friskiness, etc.). It has an internal nature or essential form that binds these qualities together and makes the squirrel a substance

2. Natures are purposive. A thing's nature establishes a purpose or goal or telos. This determines what the thing does. All things act to establish a purpose, to fulfill or actualize the potential implicit in their nature.

3. Natures are directly apprehended by the mind. The mind can somehow apprehend directly these intelligible natures or species.

4. Galileo’s Criticism: It turns out that this way of seeing things is scientifically useless. In practice, we have no access to these natures, so they can play no role in our explanations. Aristotle’s explanations were circular. Acid eats away metal because it has a corrosive nature, but corrosive simply means eats away metal.

          B. Mechanistic Reductionism: (The View of Galileo and the Scientific Revolution, The Assayer, 1623): Mechanism: The world consists of matter in motion and the mathematical laws that govern its motion. Reductionism: The qualities of complex objects, such as squirrels, persons, or countries, can be explained completely by an examination of the basic forms of the components that make them up and the  scientific laws that govern them. There is no need for recourse to an occult nature or form for the entire whole. Nor is there need for recourse to a purpose or goal that the whole is trying to accomplish apart from the blind compliance to the laws of nature. Just as a machine, such as a train, may appear to have something like soul or animating force and may appear to have purposes or goals, we can see that it is really just a combination of mechanical parts organized in such a way as to produce complex actions as it follows the rules that govern its parts.


 IV. Galileo’s Legacy. The Problems left the Post-Modern world by the legacy of the Scientific revolution. The great confidence in science as a savior of mankind had, perhaps, been replaced in the twentieth century with a growing recognition of the problems and costs of technology. Likewise, we have inherited the problems with the two intellectual components of Galileo’s legacy. Much of the world we live in is defined by the effects of these two unresolved problems.

A.      Do Science and Reason really give us absolute and complete knowledge of the world? Can all questions be solved scientifically through the application of the scientific method? Does Science oversimplify and rob the world of its beauty and grandeur? In your attempts to duplicate Galileo’s experiments you should be asking yourself  “Am I really getting nature to reveal her truths, or am I imposing my pre-conceptions onto experience?”

B.       Science and Religion II: Even after the controversies over Copernicus and Darwin have settled down, the more basic problem of whether scientific mechanism is compatible with our views of the nature and dignity of human life remains. Are human beings more than machines, and are there limitations to the applicability of the views and methods of science? Is science a savior of mankind, or are the pervasive applications of Galileo’s methods an enemy to human values.