"There never comes a point where a theory can be said to be true. The most that one can claim for any theory is that it has shared the successes of all its rivals and that it has passed at least one test which they have failed." - Phillip Kitcher

The year 2005 was a contentious one for science. The UNSW Dean of Science, Professor Mike Archer, implored educational bodies to keep Intelligent Design out of the science classroom on the grounds that it did not 'count as science'. Proponents of intelligent design replied that Darwinian evolution is 'just a theory', and thus should share equal footing with Intelligent Design and Creationism.

But what makes this debate any different from the many others surrounding scientific principles? 'Accepted' theories in science are often modified as new information is uncovered. This means that at any given time, even our best ideas are not entirely correct. After all, Aristotle once hypothesised that the earth was flat. Scientific ideas are certainly not free from criticism, but this criticism must be constructed in a manner that is consistent with the principles of scientific endeavour.

Charles Darwin's theory of evolution has never been exempt from scrutiny. In fact, it has itself evolved over time: from Lamarckian-acquired characteristics; through to Darwinian gradualism; and more recently to Gould's suggestion of punctuated equilibrium. These changes to evolutionary theory have provided fuel for the anti-evolutionist cause. Surely, if the biologists themselves cannot decide how evolution occurs, how are we (the unscientific public) supposed to accept one theory, or any theory, as a scientific truth?

Evolutionary biologists are continually confronted with the remark that Darwinian evolution is 'just a theory', as if this reprimand somehow negates arguments for evolution. However, any scientist will freely admit that everything in science, from Einstein's theory of relativity to atomic structure, is 'just a theory'. So where does this argument leave science?

Fortunately, there is no need to start mourning the death of 'real' science. On the contrary, the ability of science to deal with contending theories is one of its defining and important features. So how does one theory gain more validity than others? In science, there are strict rules that determine what a good scientific theory looks like. So the important question is whether Darwin's account of evolution is scientifically well-founded, not whether it is 'just a theory' or actually truthful.

To determine whether Darwin's account of evolution is scientifically valid, we must investigate what makes a theory 'scientific'. That is, we need to know what the rules are. As early as Parmenides and Aristotle, there was an acknowledged need among philosophers to seek a division between knowledge and mere opinion. In the twentieth century, the Vienna Circle of the 1920s developed the so-called Logical-Positivist 'verifiability criterion'. This determines the value of 'truth' in a particular statement based on the logic of its individual components. However, the Logical-Positivist methodology is not without flaws. Logical-Positivism rules out any metaphysical argument as meaningless, which has fuelled criticism of the approach.

Such criticism does not totally invalidate Logical-Positivism. But there are other problems. Karl Popper argued that is it impossible to contradict a statement using verifiability. Consider the famous example 'all ravens are black'. The only way to contradict this statement through verification is to find every raven that has existed in the history of the universe, and to show that each of them is black. Popper then argues that the natural way to demarcate science from non-science is not through verifiability, but through falsifiability. That is, if one white raven is found, the statement is refuted.

It must be acknowledged that this process of demarcation itself is contentious because there are many ways in which it can occur. However, in the 1960s, Thomas Kuhn argued that science is not simply about proving or refuting theories, but also about the need for scientists to work within established structures of knowledge. In these structures, scientists work within the theories of 'normal science' until something so different to the theory appears that there is a crisis, resulting in a transformation, a shift in belief from one theory to a replacement, and the standard of what constitutes 'normal' science shifts.

It seems, then, that there can be no black and white demarcation of science from non-science. However, we can generate a basic framework of the methodology that underpins Kuhn's 'normal science'. Good science must make claims and hypotheses based on accepted evidence. Good science also leads to further research and development of new theories. In addition, these hypotheses must be rigorously tested, and kept only if they stand up to this testing. Otherwise, they must be modified. Theories must also be based not on a single statement but must consist of many auxiliary hypotheses, which combine to form a complete theory. As the predictions of a theory are confirmed by more and more testing, it gains more and more general acceptance and becomes scientific knowledge. By these criteria, Darwin's theory seems to hold up.

... read Part 2 here soon!