Monday, July 20, 2009

A Brief History Of The Philosophy Of Science [Revised Edition]

A friend of mine recently gave me some advice: Don't let your philosophical pursuits get side-tracked by the atheism-vs.-religion debate. I pointed out that the history of modern science and modern philosophy is inextricably tied to the debate between atheism and religion. The philosophy of science has, since Descartes and Bacon, developed in explicit reaction to religious practice. The pursuit of scientific foundations has partly been the pursuit of intellectual liberation from religious dogma.

Around 1600, many rapid advancements in philosophy and science began to change the way people understood themselves and their relationship to the world. For example, Copernicus challenged conceptions of humanity by suggesting that the earth was not at the center of the universe. Galileo challenged conceptions of nature by reducing it to mathematical terms. The philosophy of science became a central issue in intellectual life.

There is a widespread misconception that science itself began during this relatively recent period in history. Of course, the most advanced, formal areas of science, such as physics and chemistry, started to take their current forms during the Renaissance. However, science, as the process of formalizing discovery, is much, much older. It probably began when the knowledge required to produce fire and tools was first communicated within communities. The Renaissance did not see the beginning of science; rather, it saw the beginning of an effort to define science as a distinct enterprise from theology.

Having seen what happened to Galileo and Bruno, Renaissance philosophers and scientists knew that, if they were going to challenge church teachings, they had better be sure their arguments rested on firm foundations. It was thus thought necessary to find ultimate principles or foundations for scientific knowledge.

Rene Descartes proposed the method of hyperbolic doubt to establish foundations of knowledge which were thought to exist independently of, but in harmony with, theology. Francis Bacon proposed the method of induction, which Sir Isaac Newton later incorporated into his Principia Mathematica.

Earlier, in the Middle Ages, theology and philosophy were one and the same. People like William of Ockam and Roger Bacon had made recognizable contributions to the philosophy of science, though we call it that only in retrospect. Of course, the Renaissance and modern era also produced great scientists who maintained strong intellectual ties to theology, including Newton. Yet, even Newton was intent on establishing principles of science which did not depend on theology or church doctrine for their validity.

Historically speaking, it is clear that modern philosophy has been heavily marked by its relationship to theology and religion. Modern science emerged as a competing form of authority, and its legitimacy was thought to be determined by the validity of its necessary principles.

This view of science persists today. Yet, ever since David Hume published his A Treatise of Human Nature in 1739, there has been good reason to doubt that absolute foundations for science can be had. Hume demonstrated that judgments about nature and cause-effect relationships do not inevitably follow from reason or observation, but are only so many habits of thought.

In the early 20th Century, the logical positivists tried to overcome this problem (known as the problem of induction) by defining religious authority out of existence. Meaning, they said, could only be scientific, because meaning is defined in terms of verification. Unlike scientific theories, religious proclamations are not verifiable. However, this argument seems to be self-defeating; for how could one verify that all meaning is defined in terms of verification?

Sir Karl Popper rejected logical positivism, promoting falsificationism as the basic philosophical principle of scientific discovery. Unlike religion, scientific theories have predictive value. That is, they can be demonstrated to be false. Their meaning is not dependent on their conditions for verification, as the logical positivists thought. Rather, their status is dependent on their conditions for falsification. Scientists do not verify theories by finding X number of examples. They thus do not depend on induction. Rather, scientists deduce predictions from theories, and test the theories accordingly. Popper thus avoided the problem of induction and the circularity of verificationism. He was able to distinguish scientific authority, not according to any indubitable foundations, but according to its ability to produce testable hypotheses about the world.

Popper's criterion remains popular among scientists today, and a common reason for rejecting religious authority is its lack of falsifiability. Yet, falsificationism has been criticized in the philosophy of science. For example, it has been observed that science does not always proceed by clear-cut cases of falsification. When data contradicts theory, ad hoc adjustments are often made. Also, problematic data is sometimes ignored for any number of reasons: it may be dismissed as a statistical outlier, or it is thought to be the result of human error or faulty equipment. While falsificationism helps us understand what distinguishes science from religion in theory, it does not explain how science always proceeds in the real world.

According to Thomas Kuhn, scientific advancement is most dramatically made when new paradigms change the way we interpret the data. Scientific theories are not abandoned because of falsifying data. Rather, they are replaced by new ways of thinking which change the way that data is understood. This view is not necessarily opposed to falsificationism, however. We might say that paradigm shifts are justifiable precisely because new paradigms have more predictive value.

Then Paul Feyerabend argued that science does not advance according to any fundamental rules or methods at all. In fact, he said, what people think of as "science" is a myth. He thus advocated an anarchistic, "anything goes" approach to science.

Finally, neo-pragmatists like Richard Rorty (following Wittgenstein) said there was no such thing as scientific advancement at all; at least, not if we think of scientific progress in terms of getting closer and closer to some absolute Truth-with-a-capital-"T." New scientific theories are just new ways of talking. There is no absolute, extra-theoretical standard to judge, for example, whether Einstein's theory of gravity is better than Aristotle's. Einstein and Aristotle spoke different languages, and we adopt yet another language when we compare them. Thus, there are no absolute foundations. No indubitable standards for measuring progress. No all-encompassing methods or principles. There is only language and how we use it. As Wittgenstein said, language is a tool with innumerable functions, and its meaning is how it is used.

While this may seem to undermine the validity of science, the opposite is the case. It does not undermine any supposed foundations which scientists depend upon for their work. On the contrary, it undermines the motivation for looking for ultimate foundations. This proves to be as much of a liberation from religious dogma as anyone could want; for the lack of foundations here applies as much to religion as it does to science.

The "modern" sciences have become dominant forces in the world, largely thanks to political as well as scientific advancements. Their formal tools and methods have produced previously unimaginable developments, ever broadening the scope of human understanding. Scientists rarely feel any pressure to justify their practices, no longer feeling the need to appeal to ultimate foundations. The tangible results of the process are where justification is found. Meanwhile, religion is struggling to maintain its status as a legitimate form of authority.

Science and religion are still competing forms of authority. Many people like me, not all of them self-described atheists, reject religious authority as unfounded and regard every aspect of our existence as being open to discovery. We are derided as followers of "scientism" or "naturalism." Our detractors claim that naturalism requires faith in the methods and principles of science. They say religion is better than science when it comes to informing our lives, because it rests on the firm, absolute foundation of God's will. They say science cannot answer important questions, that science cannot explain important aspects of our lives, such as the very desire to search for meaning in the universe.

These objections are all of them unfounded. The appeal to God's will has no discernible meaning. The demand for foundations is itself unfounded. There is therefore no basis for excluding any aspect of experience from science's grasp. We cannot decide ahead of time what is or is not open to formal discovery. Science is dynamic, disparate, and evolving. Perhaps its most salient feature is its theoretical unpredictability.

Of course, science does have recognizable general features. There are standards that scientists generally adhere to, such as logical consistency, Ockam's Razor, and Popper's criterion of falsifiability. However, these are not absolute foundations. They do not establish the ultimate legitimacy or authority of any science. Rather, they describe aspects of formal discovery. Consistency, parsimony, and falsifiability are guiding principles scientists try to follow. Ockam's razor and logic help maintain the integrity of formal discovery, while falsificationism reminds scientists that success depends on the value their theories can demonstrate.

The point is, scientists do not have faith that any particular methods or principles work. Rather, scientists simply develop and use new methods and principles because they produce tangible results. Scientific progress is made when new methods of discovery are adopted, methods which replace or expand upon the methods previously used. Scientific theories are adopted, not believed. When we say that a scientific theory is "true," we only mean that it works. We do not believe in science as a matter of faith. We use it as a matter of practice.

Scientific knowledge is not just a collection of theories; it is the practical abilities engendered by theoretical frameworks. The meaning and value of science is determined by the results of its practice, and not in the search for its foundations. There is no need to look for absolute foundations, and there is no reason to wonder why none were ever found. The outcome of scientific discovery is its continuously developing foundation.

The burden of proof is not on science to justify itself. In fact, there is no single belief system or institution called "science." There is thus nothing to justify as such. There are many scientific methods and institutions, and there will be many more, and we have every right to call them into question. However, if we do so, we must have a reason. What reason do critics of science have for questioning its practices? How do they justify their authority to question science?

Appealing to God no longer gets the job done.

The success of the Enlightenment was not in establishing firm foundations for scientific knowledge. It was in revealing the lack of absolute foundations for knowledge in general, including theistic knowledge. Modernity's greatest triumph was not just in furthering the sciences, but in freeing discovery from the restrictions of religious authority. That is progress.