From Philosophy to Science
All the sciences—astronomy, physics, chemistry, biology—had their origins in, and eventually broke free from, philosophy. Before astronomy and physics existed as sciences, for example, philosophers speculated about the arrangement of the natural universe by starting from assumptions about God or some other ideal standard and reasoning to conclusions about the way the universe must be. For example, if all important events seemed to occur on the Earth, then the Earth must be the center of the universe. Since a circle is the most perfect shape, the sun must travel about the Earth in a circular orbit. The moon must travel in another, closer, circular orbit, and the stars must be in a sphere, the most perfect three‐dimensional form, around the whole. (To this day, the sun, the moon, and the stars are called heavenly bodies, because they were supposed to be perfect.)
The sciences of astronomy and physics were born when individuals began trying to understand natural objects and phenomena by observing them. When Galilei Galileo (1564–1642) trained a telescope on the moon, he observed that its crater‐scarred landscape was far from the perfect sphere the philosophers supposed it to be. Contributing to physics also, Galileo recorded the motion of falling objects by rolling a ball down a chute. In describing his findings, Galileo helped invent the modern notions of velocity and acceleration. Isaac Newton (1642–1727) added concepts like force and inertia to create a powerful descriptive scheme for understanding motions of bodies on the Earth as well as heavenly bodies such as the moon.
In creating the science of physics, Galileo, Newton, and other thinkers of the Enlightenment broke with philosophy. Philosophy reasons from assumptions to conclusions. Its arguments take the form, “If this were so, then that would be so.” Science proceeds in the opposite direction: “This is observed; what could be true that would lead to such an observation, and what other observations would it lead to?” Philosophical truth is absolute; as long as the assumptions are spelled out and the reasoning is correct, the conclusions must follow. Scientific truth is always relative and provisional; it is relative to observation and susceptible to disconfirmation by new observations. For a long time, astronomers thought there were only seven planets, but then an eighth and a ninth were discovered. Philosophical assumptions concerned abstractions beyond the natural universe: God, harmony, ideal shapes, and so on. Scientific assumptions used in theory‐building concern only the natural universe and the way it might be organized. Though Newton was a theologian as well as a physicist, he separated the two activities. About physics, he said, “Hypotheses non fingo” (“I do not make up hypotheses“), meaning that when studying physics he had no concern for any supernatural entities or principles—that is, for anything outside the natural universe itself. The reason the ocean has tides is not God’s will but the gravitational pull of the moon as it revolves around the Earth.
As well as physics, the ancient Greeks speculated about chemistry. Philosophers such as Heraclitus, Empedocles, and Aristotle speculated that matter varied in its properties because it was endowed with certain qualities, essences, or principles. Aristotle suggested four qualities: hot, cold, wet, and dry. If a substance was a liquid, it possessed more of the wet quality; if a solid, more of the dry. As centuries passed, the list of qualities or essences lengthened. Things that grew hot were said to possess the inner essence caloric. Materials that burned were said to possess phlogiston. These essences were considered real substances hidden somewhere within the materials. When thinkers turned away from speculation about hidden essences and began making and inter‐relating careful observations of material change, chemistry was born. Antoine Lavoisier (1743–1794), among others, developed the concept of oxygen from the careful observation of weights. Lavoisier found that when the metal lead is burned and transformed into a yellow powder (lead oxide) in a closed vessel, the powder weighs more than the original metal, and yet the entire vessel retains the same weight. Lavoisier reasoned that this could occur if the metal combined with some material in the air. Such an explanation contained only natural terms; it left out the hidden essences suggested by philosophy and established chemistry as a science.
Biology broke with philosophy and theology in the same way. Philosophers reasoned that if living and nonliving things differed, that was because God had given something to the living things He had not given to the nonliving. Some thinkers considered this inner thing to be a soul; others called it vis viva (life force). In the seventeenth century, early physiologists began looking inside animals to see how they worked. William Harvey (1578–1657) found what seemed more like the workings of a machine than some mysterious life force. It appeared that the heart functioned like a pump, circulating the blood through the arteries and tissues and back through the veins. As in physics and chemistry, such reasoning left out the hypothetical assumptions of the philosophers and referred only to observations of natural phenomena.
When Charles Darwin (1809–1882) published his theory of evolution by natural selection in 1859, it created a furor. Some people were offended because the theory went against the Biblical account of God creating all the plants and animals in a few days. Darwin even shocked some geologists and biologists. Familiar with the overwhelming fossil evidence of the rise and extinction of many species, these scientists were already convinced that evolution occurred. Yet although they no longer took the Biblical creation account literally, some of them still regarded the creation of life (hence, evolution) as the work of God. They were no less offended by Darwin’s theory of natural selection than were those who took the Biblical account literally.
Darwin’s theory impressed his contemporaries because it offered an account of the creation of life forms that left out God or any other nonnatural force. Natural selection is a purely mechanical process. If creatures vary, and the variation is inherited, then any reproductive advantage enjoyed by one type will cause that type to replace all competitors. Modern evolutionary theory arose in the first half of the twentieth century when the idea of natural selection was combined with the theory of genetic inheritance. This theory continues to arouse objections because of its godless naturalism.
Just as astronomy, physics, chemistry, physiology, and evolutionary biology broke with philosophy, so psychology broke with philosophy. Psychology’s break was relatively recent. Until the 1940s few universities had a separate department of psychology, and professors of psychology were usually to be found in the philosophy department. If evolutionary biology, with its roots in the mid‐1800s, is still completing its break with theological and philosophical doctrine, it is no surprise that today psychologists still debate among themselves about the implications of calling psychology a tr...