The philosophy of science seeks to clarify the objectives and means used by scientists, and what is the reliability of scientific theories. Science is popularly viewed as a cumulative and progressive activity. However this view has profound philosophical implications, and in fact the effort to define the nature of science is in itself part of the history of philosophy.
Aristotle‘s writings on nature make him the world’s first real scientist, though his conclusions have long been superceded. His contributions are so great that he stands alongside Plato as one of the greatest thinkers of the ancient world. He said, in contrast to Plato, that the material world is real and not a creation of eternal forms. He taught that individual things combine form and matter in ways that determine how they grow and change. Aristotle was also the founder of formal logic.
During the 12th century a revolution took place that completely changed the course of Western philosophy. The writings of Aristotle were translated into Latin and were studied by churchmen for the first time. They gave teachers access to his scientific works and to his logical method of argument. The `Metaphysics’ of Aristotle was especially influential in turning philosophers away from Plato. The scientific writings prompted research into the natural world by such men as Roger Bacon.
One of the early writers on scientific method was the English philosopher and statesman Francis Bacon, whose New Organon appeared in 1620. He proposed induction as the logic of scientific discovery and deduction as the logic of argumentation. He denounced reliance on authority and verbal argument and criticized Aristotelian logic as useless for the discovery of new laws. Bacon called for a new scientific method based on inductive generalization from careful observation and experiment. He was the first to formulate rules of inductive inference.
He believed that there was a rigorous “organ,” or method, for making scientific discoveries, but his theory of method was quite different from that of Descartes. Bacon believed that instead of analyzing intuitive ideas, scientists should first empty their minds of all preconceptions and then make observations. By using inductive logic one could generalize from these observations about particular cases. Thus one would finally arrive at the most fundamental and comprehensive laws of nature. The view that all scientific knowledge is derived from observation alone, is called empiricism (empeira is the Greek word for “experience”).
Bacon’s theory may seem much more plausible than Cartesian rationalism, especially to Anglo-Americans who have been brought up in an culture strongly influenced by empiricism. However, Bacon’s approach has serious inadequacies.
In his Discourse on Method (1637), the French mathematician and philosopher Ren� Descartes wrote that theoretical science should be like Euclidean geometry. A science such as physics should be based on ‘first principles’ comparable to the axioms of geometry, which were discovered and validated through the systematic analysis of intuitive ideas. Descartes thought, for example, that the law of inertia could be seen to be true through the use of reason alone. The view that science can be based on principles that are revealed through introspection, is called rationalism (from the Latin ratio, “reason”). He wanted to account for observed phenomena on the basis of what he called clear and distinct ideas — the method of deductive reasoning. He followed Bacon and Galileo in criticizing existing methods and beliefs, but unlike Bacon, who argued for an inductive method based on observed facts, Descartes made mathematics the model for all science, applying its deductive and analytical methods to all fields.
During the Renaissance a preoccupation with mathematics and natural science began that endured for two centuries. In the Enlightenment era of the 17th and 18th centuries, attention turned to the nature of the human mind and its abilities to master the natural world. The two main philosophical points of view were rationalism and empiricism. Then, at the end of the Enlightenment, appeared the work of Immanuel Kant, who tried to bridge the gap between rationalism and empiricism. With him the Enlightenment ended and the 19th century began.
The German philosopher Immanuel Kant combined the empiricist principle that all knowledge has its source in experience with the rationalist belief in knowledge obtained by deduction. According to Kant, the underlying nature of reality cannot be known — only the appearances of everything (which he called phenomena) can be perceived. People, however, impose a form of reality on the world by the way they organize their thoughts about it. They thus impose an order on their world through categories created by the mind. Although the content of experience must be discovered through experience itself, the mind imposes form and order on all its experiences, and this form and order can be discovered a priori, that is, by reflection alone. Philosophers in the tradition of Kant have argued that it is impossible to make observations that are free of all preconceptions, because all observational reports go beyond what has actually been perceived — in modern terms, all observations are “theory-laden.”
During the 17th century — the era of Galileo Galilei, William Harvey, Sir Isaac Newton, and Robert Boyle — scientists and philosophers alike were convinced that with the help of the newly discovered scientific method modern scientists would quickly surpass the achievements of their Greek and medieval predecessors. Disagreement existed, however, as to the details of the correct scientific method. The work of Galileo was of great importance in the development of a new world view. Galileo brought attention to the usefulness of applying mathematics to the formulation of scientific laws. This he accomplished by creating the science of mechanics, which applied the principles of geometry to the motions of bodies. The success of mechanics in discovering reliable and useful laws of nature suggested to Galileo and to later scientists that all nature is designed in accordance with mechanical laws.
Modern Views on Science
Bacon and Descartes were trying to provide a simple, fail-safe method for scientific study. The modern view of the nature of the scientific method is that both experience and reason — induction and deduction — play an important role in science. Creative reasoning, or imagination provides speculative hypotheses; experience helps weed out those which are false.
Science may be broadly defined as the development and systematization of reliable knowledge about the physical universe. Science is the objective pursuit of reliable knowledge. Although one might “know” something through authority, faith, or intuition, scientific method is distinct in that it must be possible for other investigators to ascertain the truth of scientific theories. Its founded on objective observation, logical reasoning, the formulation of hypotheses that fit the data and predict other posibilities, repeatable experiments that can fail as well as succeed, and analysis and review by the scientific community. Scientific method involves the interplay of two kinds of reasoning: inductive, and deductive.
- Inductive reasoning
- Reasoning from the particular to the general; from specific observations and experiments to more general hypotheses and theories. Drawing conclusions from various facts or observations, e.g. the Sun will rise tomorrow morning because it did every morning I have experienced. Foundation for probability theory and statistics.
- Deductive reasoning
- How one statement may be said to follow from others, as a consequence. The study the validity of inferences by virtue of their structure, not content. Reasoning from theories to account for specific experimental results.
However, no scientific theory, regardless of how well it has been tested, can be considered infallible. Nevertheless, methods have been developed to criticize and test such theories and to eliminate bad ones.
Testing Scientific Theories
Deductive fallacies have been known since ancient times. Less well known and more recently discovered are what might be called inductive fallacies. A simple example is the fallacy of using irrelevant data, which Bacon illustrated with the following story:
|…it was a good answer that was made by one who, when they showed him hanging in a temple a picture of those who had paid their vows as having escaped shipwreck, and would have him say whether he did not now acknowledge the power of the gods — “Aye,” asked he again, “but where are they painted that were drowned after their vows?”|
The basic conjecture to be tested is “If one makes a vow during a storm at sea, then one will not be drowned”. The proposed method for collecting data either to support or to refute the conjecture is as follows: go to churches and record instances of people who paid their vows as thanks for having escaped drowning. The instances so collected, appear at first to confirm the conjecture. Evidence that would refute it, is logically impossible to find, given the method of collecting data.
One of the basic principles of scientific testing can therefore be stated roughly in the following manner: the outcome of a certain test cannot confirm a theory unless it is logically possible that there could be another outcome that would have refuted the theory.
Conjecture and Refutation.
Any agreement of a conclusion with an actual observation does not itself prove the correctness of the hypothesis from which the conclusion is derived; it simply renders the hypothesis that much more plausible. The scientific process begins when observations clash with existing theories or conjectures; then a new theory is proposed and the logical consequences of the theory (hypotheses) are subjected to rigorous empirical tests. The objective of testing is the refutation of the hypothesis.
An important characteristic of a scientific theory or hypothesis is that it must be falsifiable. This means that there must be some experiment or possible discovery that could refute the theory. When a theory’s predictions are falsified, new hypotheses are devised and tested until a new theory emerges. Those theories that survive falsification are said to be corroborated and are tentatively accepted.
A theory gains exceptional credibility if it predicts something unexpected. Einstein’s theory of gravitation predicted in advance of experiments that light would be deflected by passing close to a strong gravitational field. At the time it was thought that light should be unaffected, but observations during a total solar eclipse showed that stars could be seen which should have been hidden by the sun.
Pseudo-science typically expounds its claims in such a way that they are very difficult or impossible to subject to tests which might lead to contradictory evidence; a psychic might claim for example that the presence of electronic recording devices offends the spirits.
A corroborated hypothesis is one whose predictions have been verified. It becomes highly corroborated if further corroborated by subsequent tests, and it is then considered to be reliable knowledge. A scientific fact is a highly corroborated hypothesis that has been so repeatedly tested and for which so much reliable evidence exists, that it would be perverse or irrational to deny it.
The ultimate test of the validity of a scientific hypothesis is its consistency with the totality of other aspects of the scientific framework. This inner consistency constitutes the basis for the concept of causality in science, according to which every effect is assumed to be linked with a cause. A scientific theory is a unifying and self-consistent explanation of fundamental natural processes or phenomena that is totally constructed of corroborated hypotheses.
Truth and Reality
To what extent can we say that scientific theories are ‘true’? (Assuming for the moment that we share some common idea of what ‘truth’ means…)
Science is not about “proving true things” about the world. Proof and truth are mathematical concepts, applicable only to mathematics. In science, we can never be completely sure that any theory is ‘absolutely true’; only that it fits well with the evidence so far. Tomorrow, an exception could be found that ‘disproves’ the theory. Scientists like to think that their theories get closer and closer to some abstract ‘truth’ about reality, but none (that I can conceive of) would ever claim that their theories are the final word. Scientists never claim that a theory is “proved” in a strict sense; they prefer to use the word “corroborated” rather than “proved”.
If someone says that matter is made of tiny particles that they call ‘atoms’ that are too small to see, why should we believe them? The short answer is that many, many different experiments have produced results consistent with the idea, while none have ever shown otherwise. Atoms are routinely ‘smashed’ in particle accelerators in laboratories around the world. The idea works.
Questions about the reality of our theoretical models are especially vexing at scales above and below our everyday experience, as in astronomy and physics at the sub-microscopic level. In quantum mechanics, for example, the theories suggest that atomic particles sometimes behave like particles, and sometimes behave like waves, and we can never be quite sure where they are and how fast they are moving; instead, we can only treat them as being smeared out into a probability distribution or a ‘wave function’ that collapses to a specific value when a measurement is made. For some scientists, the logical conclusion of these theories is that measurements generate multiple universes, with different results in each; other scientists question the reality of those universes, supposing instead that they are mathematical conveniences only. And now some scientists are claiming that the sub-atomic particles are ultimately made up of vibrating ‘strings’…