R M Cullen
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Most dictionaries define science as (or very close to) “the intellectual and practical activity encompassing those branches of study that apply objective scientific method to the phenomena of the physical universe. The knowledge gained by the activity”.
There are two key parts to this definition. The study must involve the physical universe and it must use scientific method, which has two limbs – observation and experiment. Experiments aim to test predictions and to distinguish between competing explanations (by falsifying one or more of them).
Competing ideas are a feature of science. There are often multiple ways of explaining an observation. There are a number of tools scientists use to decide between competing ideas. The most well known is the experiment, where conditions are set up to test explanations. If ‘A’ is true this will happen. If ‘B’ is true that will happen.
Ideas are proved objectively in science. That is, the observations and experiments can be repeated by other scientists under the same conditions in different parts of the world.
This is the key ‘way of knowing’ difference between science and religion. Proof by revelation (truth revealed by God to individual men or small groups) is a cornerstone of many faiths, and these episodes of contact with the deity are often recorded.
Proof by revelation has no place in science. The appearance of life on Earth may have happened exactly as this is recorded in the Book of Genesis, but scientific proof of it must be obtained from repeated observations and experiments.
“This is true because God told that person (or me) it is true” carries no weight at all in scientific discourse.
On the other hand it is dishonest of atheist scientists to claim that science, as a matter of definition, is only concerned with non-supernatural explanations for the phenomena of the physical universe. Science is about finding the truth. If as the result of applying scientific method, it turns out that God created it, or the Vogons destroyed it, then that is the answer according to science until better observations are made, or the result is overturned by further experiments.
This last is vitally important. All knowledge in science is provisional, as the answers produced by application of the scientific method are approximations to the truth. Much of what we believe today will not be believed in 100 years time.
Scientific knowledge is based on observation, not on an appeal to authority.
The story of Galileo and the Leaning Tower of Pisa is often told, and may even be true. Aristotle held that objects fall at a speed proportional to their weight. So a 2kg ball will fall at twice the speed of a 1kg ball. Galileo dropped balls of different weights from the Leaning Tower of Pisa and they hit the ground at the same time.
So, at its simplest, science is about building up a library of observations, developing theories to explain those observations, and performing experiments to eliminate all theories bar one.
The development of theory from observations is done by induction. Induction argues from the specific to the general. If a large number of observations, all consistent with the proposed theory, are made under a wide variety of conditions, then the proposed theory is said to be 'confirmed by' or 'consistent with' observations.
However, induction is not certainty. An inductive truth is only valid until the first contrary observation.
For example, I may travel around the country and see only white sheep wherever I look. From these observations I might conclude 'all sheep are white'. The next day I see a black sheep. Theory disproved. Totally.
The philosopher, Bertrand Russell, provides a more gruesome example with his tale of the inductivist turkey who observes that he is fed every day at 9am, whether it is fine or wet, whether it is summer or autumn, The turky concludes "I am fed at 9am". Unfortunately this theory is disproved when on Christmas Eve the farmer approaches the turkey with an axe.
Some theories explain nothing because they are consistent with any observation. Karl Popper introduced the notion of falsification into the philosophy of science. His position was that, in order to qualify as a scientific theory, a candidate theory had to be falsifiable (testable). That is, it had to make predictions which an appropriate experiment could show were false.
In Popper's view, scientific theories are not true. They are the best available, or the one not yet falisified, or even the one least falsified.
Premiss: Force equals mass times acceleration
Premiss: mass = 1kg. Acceleration equals 1 metre per second per second
Conclusion: a force of one newton has been applied
This is a logically sound argument. The truth of the conclusion depends on the truth of the premisses.
Kuhn proposed that what he calls 'normal science' is practiced within a paradigm or set of theories and experimental approaches accepted by 'normal scientists'. Over time normal science accumulates falsifications and problems unanswerable within the paradigm until a crisis develops. Crises are resolved by revolution, the adoption of an entirely new paradigm by more and more scientists. This new paradigm becomes 'normal science' and the cycle continues.
Imre Lakatos can be seen as breaking down Kuhn's paradigms (which he called research programs) into their hard core, their protective belt, their positive heuristic, and their negative heuristic
The hard core of a science consists of the central shared beliefs of normal scientists. Theoretical positions that are not open to challenge.
The protective belt consists of additional hypotheses which supplement the hard core and protect it from falsification in the sense that any accepted falsifiying observations can be dealt with by modifying the protective belt, leaving the hard core intact
The negative heuristic of a research program specifies the things a scientist can not do (such as challenging the hard core) while remaining part of the research program.
The positive heuristic consists of ways of being and ways of doing within the research program which are approved by normal scientists and lead to recognition and advancement witihn the program.
Alan Chalmers. What is this thing called science?. This is the classic introduction to the philosophy of science. The third edition was published in 1999
Alan Chalmers, Science and its fabrication Published in 1990
In a more general sense, the field of sociology of science, and writers such as Feyeraband and Foucault will help to break down any idea that science is different from any other field of human activity or that 'scientific knowledge' is 'better' than other ways of knowing.
Science is what scientists do. Scientists are people, and science has all the flaws of any other human activity - competition for limited resources, personality clashes, desire for recognition and authority, patronage, fraud. It's a long list.