What is science?

At first blush, this question seems easy to answer. Science includes things like physics, astronomy, chemistry, and biology—disciplines that investigate the natural world. However, there are other disciplines that also investigate the natural world but are widely agreed to be unscientific: astrology (the study of how stars and planets supposedly foretell or influence human affairs), homeopathy (a type of alternative medicine claiming that sick people can be cured by toxic substances that would cause similar symptoms if given to healthy people), and phrenology (a field of study purporting to explain psychological characteristics by the shape of a person’s skull), to name a few. These disciplines are rejected by the mainstream scientific community and are usually classified as pseudoscience—things that resemble science in some ways, and may be regarded as scientific by their practitioners, but really do not belong in the category of genuine science.

Sciences Pseudosciences
Astronomy
Biology
Chemistry
Physics
Psychology
(etc.)
Astrology
Homeopathy
Alchemy
Phrenology
Psychoanalysis
(etc.)

To truly understand what science is, we need to know why some disciplines belong in the “science” category, and why others don’t. In other words, we need to know the necessary and sufficient conditions that make something scientific.

Unfortunately, identifying the necessary and sufficient conditions for science turns out to be much harder than one might expect. It is difficult to formulate a precise definition of science in terms of necessary and sufficient conditions, because—as we’ll see in Chapter 11—there doesn’t appear to be any distinctive set of features shared by all and only the sciences. The challenge of formulating necessary and sufficient conditions for science is known as the demarcation problem, and to this day it remains one of the greatest unsolved problems in the philosophy of science. We’ll return to the demarcation problem later. For now, let’s simply take for granted the commonsense view that disciplines widely regarded as paradigmatic examples of science—physics, astronomy, chemistry, biology, and so on—really do differ in important ways from astrology, homeopathy, and phrenology.

We’ll learn more about the nature of science by studying the histories, theories, and methods of scientific disciplines. For this reason, further discussion of the demarcation problem will be postponed until chapter 11. Meanwhile, let’s begin our journey into the world of science with a brief look at the historical inception of modern science, a scientific “revolution” in which the Christian faith played a pivotal role.