It often seems that skeptics and fellow-travelling rationalists and freethinkers are engaged in a perpetual holding operation, building dams and levees to hold back the flood of unreason in particular areas where we concentrate our limited resources. Meanwhile other forms of superstition flourish and it is likely that the sum total of unreason in the world has not been diminished by the supposed triumphs of Science and Reason in the last century or two. If this is indeed the case, then it is easily explained because the dominant conceptions of Science and Reason have been defective. Popper and Bartley have corrected this situation and their ideas have the capacity to drain the swamp of unreason and lower the general level of prejudice, instead of just holding it back in some places.

The Evolutionary Approach to Knowledge

Popper has helped to revive the evolutionary approach to knowledge. This approach, labelled 'evolutionary epistemology', was very popular last century but it disappeared when the methods of physics became the major concern of the philosophy of science.

Evolutionary epistemology applies the principle of natural selection to scientific theories and other forms of knowledge. It is concerned with problem-solving and error-elimination under various forms of selective pressure. In contrast, most schools of philosophy are concerned with the foundations of belief, the probability of theories, or merely exploring the meanings of words.

Popper started with the old idea that knowledge grows by trial and error, or in more learned terms, by conjecture and refutation. He extended this perspective using a four-stage problem-solving model to describe the evolution of life on earth, the growth of knowledge and the activities of organisms from the amoeba to Einstein.

The starting point is a problem situation confronting the organism; the second step is the production of tentative solutions and trial responses to the situation. The third stage is the process of error elimination, weeding out those among the tentative solutions that do not work. The fourth stage is the emergence of new problems or perhaps the reformulation of the original problem.

Popper's schema differs in an important way from the traditional "nature red in tooth and claw" picture of evolution in which the driving force was supposed to be the pressure of competition in the battle for survival. In Popper's model the progressive impetus does not come from the external pressure of the environment, instead it springs from the capacity of the organism to generate variations in form or behaviour, or, in the case of humans, to create ideas, including imaginative myths, stories, and scientific theories.

In science the error-elimination stage consists of critical discussion and experimental tests. Testing of course involves observations and the four-stage schema challenges the common view that scientific problem-solving begins with observation or the collection of data. This impression is heightened by the practice of shooting rockets into outer space to observe things (like the extra moons of Uranus) that have never been seen before. There is a tendency to think that if we collect enough information, true theories will emerge from them.

The giant Messell texts that form the basis of the secondary science course in NSW used to tell us the following (and may still do so):

'Science advances in a definite pattern. First and foremost scientists must make observations. These observations must be careful and accurate; and the results of more and more observations accumulate".

Apparently Messel is one of the people who Colin Tudge would like to have fried in rancid yak fat. It is painfully true that observations accumulate but the notion that this constitutes the growth of knowledge is false and dangerous. It is logically and psychologically impossible to make any observation without a point of view (about what to observe). As Darwin wrote in one of his letters "How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service".

It is pointless and wasteful to do experimental work without explicit and self-conscious reference to the scientific problem situation and the state of the debate between rival theories. Attempts to achieve the "ideal procedure", the "advance in a definite pattern" described in the Messel text would make the scientist repress their imaginative and critical facultues to the level of a Creation Scientist, or to a recording machine.

People who think that science consists of accumulated data are likely to be surprised when they find that just about all the evidence that scientists use to describe evolution can be used (in odd ways) to fit into the very different theories of Creation Scientists.

Another opening for Creation Scientists is provided by unsolved problems in the scientific account of evolution. Of course these do not challenge the basic idea of evolution, rather they concern details and mechanisms. People who think that science is a firm structure of authoritative knowledge become confused and worried when Creation Scientists reduce unwary scientists to embarrassment by pressing and probing at open problems, often in areas where the scientists are not expert. Due to the vogue of over-specialisation many scientists are not equipped to handle a wide-ranging debate and Creationists have been able to exploit this.

It is important to explain that knowledge grows in response to unsolved problems or open problem situations. The problem-solving process starts with problems , with the realisation that we do not know everything. This realisation is supposed to be the beginning of wisdom; it is certainly the beginning of the process that leads to the growth of scientific knowledge.

Open problems in evolutionary theory concern the detailed steps in parts of the evolutionary tree where fossil records are scanty, and the time-scale for some of the steps and stages in the sequence of forms. Other open problems concern the relative contributions of the three major factors that account for the differentiation of species (mutation, selection and migration) in specific cases.

It must be understood that scientists do not need to apologise for the existence of open problems. They are the growing points of science and if at any time none exist then they have to be created by critical appraisal of existing theories and by experimental tests. Of course this sounds like the pinnacle of absurdity to people who believe in their favorite theory, who hate to see their ideas subjected to criticism. But good ideas stand up to criticism, they pass their tests. And if they fail, then we have learned something important.

Some of the things that I have been saying can be summed up by two contrasting images of scientific knowledge. The conventional view tends to regard science as an edifice of well based theories (justified beliefs). The alternative view regards theories as imaginative constructs, freely created, to be subjected to tests. They are never final, never conclusively justified, though we can usually form critical preferences between rival theories in the light of the evidence and arguments produced up to date.

The dogmatic view of science can be depicted in an architectural image. Science is like a house that needs firm foundations to hold it up. The edifice of scientific knowledge is based on facts and observations. Scientists are like bricklayers who build layer by layer, brick by brick, accumulating their observations, carrying out their experiments, meticuously noting the results in their note books to add a brick or two to the walls. According to this theory we need to build on the rock of verififed observations otherwise the vast structure of inference and reasoning may fall down.

The more appropriate image is that of a helium or hot-air balloon that floats in the air while remaining tethered to the earth by a string or mooring lines. The 'earth' is the empirical base of observations, experimental tests and practical applications. An example of a mooring line was Eddington's eclipse observations which provided a crucial test between Newtonian theory and Einstein's relativity. These observations cannot be regarded as a source of relativity theory because they were made after Einstein created the theory and deduced various consequences from it. Nor can Eddington's data be regarded as positive confirmation of relativity because Einstein's theory has been revised since that time.

Evidence and observations do not hold the balloon up, like the foundations of an edifice, instead they stop it from floating away, as it will do if people lose interest in experimental tests, in Popperian falsifications, "bouncing ideas off reality" as Colin Tudge put it. People who believe in foundations want to bring the balloon down to earth by filling it with the ballast of observations so that the mooring lines shrink and turn into proper foundations. However the balloon of science does not need to be brought to earth, so long as the mooring-lines remain intact. Instead the balloon needs to be driven higher into the air by the 'hot air' of speculative thought, by bold conjectures that drive our understanding over the frontiers of knowledge. These conjectures need to be controlled but not stiffled by imaginative criticism and tests.

It must be understood that scientific knowledge is tentative and provisional, it cannot be established as a body of dogma. Admittedly some features of the world are so well tested, so well probed, explored and criticised that they are to all intents and purposes settled. The debate has moved on beyond these matters. Among these are the notion that the planets go around the sun and not vice versa, also that life evolved by stages from primitive beginnings. These views are not dogmas as the Creationists claim, they are simply so well tested in decades of research and controversy that radically new information and arguments would be required to re-open a debate over them. Meanwhile spirited debate rages over the steps, history and mechanisms at work in cosmology and evolution.

The notion that science consists essentially of piling up data, adding bricks to the well founded edifice, has created serious problems both inside and outside science. Many scientists do not understand the need to have competing theories, the need for open problem situations, for experiments that perform the role of tests instead of verifications and the need to periodically examine philosophical first principles.

The edifice theory promotes over-specialisation. If we advance by accumulating data then the more we accumulate in a narrow field, the better we will get ahead. But problems usually ignore boundaries between fields and disciplines. The poacher often gets the fattest rabbits, as Watson and Crick demonstrated in their work on the structure of DNA.

Over-specialisation in turn has made it harder for laypeople to come to grips with science and to retain a healthy and critical attitude towards experts and specialists. If years and years of study are required to get to the frontiers of knowledge, how can an outsider challenge the opinion of people who have spent their lives piling up bits of information in the field? The answer is to follow the advice of Jacques Barzun in The House of Intellect:

'With a cautious confidence it is possible to master the literature of a subject and gain a proper understanding of it: specifically, an understanding of the accepted truths, the disputed problems, the rival schools and the methods now in favour. This will not enable one to add to what is known, but it will give possession of all that the discipline has to offer to the world.'

The emphasis on merely "getting the facts" has blunted the sense of intellectual adventure of scientists and also their sense of moral responsibility. If the highest duty of the seeker for Truth is to carefully record observations, where is the scope for reflection on the value and the purpose of the project in hand? It may as well be a project to grow food or to make bigger and cheaper bombs. The project may be completely out of touch with the live scientific problems in the field and with the practical needs of the community.

The edifice concept of science, aided by over-specialisation, has produced a breakdown in communication between the sciences and the humanities, described by C. P. Snow as 'the two-culture problem'. In addition, the traditional (inductive) view is closely related to the bucket theory of mind which is envisaged as a passive receptacle to be filled with information from the world outside. This view has created a backlash from poets and Romantics with William Blake in the lead. They will not accept a theory of science and the human mind which obliterates creativity.

Thus defective theories of science have alientated several generations of poets from science and in many instances from rationality as well. This is a cultural disaster and Popper's correction to these ideas should earn him our profound gratitude if he had made no other contribution to philosophy beyond the return of the creative imagination to its place at the heart of science.

Many forms of unreason such as Creation Science feed on error, on defective theories of science, including the idea that science consists of an edifice of beliefs that are verified or justified by a process of induction. This has been the orthodox view for over a century, so Creationists and others have had plenty of support from people who appear to be their enemies. Karl Popper has corrected many misleading ideas which confuse both scientists and the lay public about the way that science advances and the way that productive scientists use evidence, imagination, logic and criticism in harmonious combination.

For maximum impact Popper's ideas need to be linked with William Bartley's non-dogmatic theory of rationality. This corrects the tendency to dogmatism that haunts the mainstream of philosophy from Plato through Bertrand Russell to the present. Bartley's ideas deserve a full exposition in the literature of skepticism: in the meantime the works of Popper need to be better known and applied to the teaching of critical thinking as suggested in the Appendix to this article.

The study of critical thinking that is proposed here could be taught at school, it could be used for an introduction to university courses in philosophy, it could be a core subject for all tertiary students. Its content could be adjusted for the interests and capacities of the class and it offers an alternative to the debacle of general studies where students of marketing and organic chemistry have to shuffle and fidget for a certain number of hours in lectures on Introductory Psychology or Medieval Drama. The course would consist of exploration and applications of the four methods of criticism to any theories or beliefs which interest the class.

The test of evidence and experience could lead to the philosophy of science, to a study of rules of evidence in law, to the use of diagnostic tests by doctors, motor mechanics or plumbers, and to the use of clues by detectives and archeologists.

The test of comparison with other theories would raise questions about the weight and authority to be assigned to assumptions imported into arguments, more or less uncritically, from other domains. For example the psychological theories assumed by literary critics, the physical theories assumed by geologists, the sociological theories assumed by engineers, the economic theories assumed by politicians. This part of the course should open student's eyes to the inter-dependence of the so-called disciplines and with any luck the artificial nature of boundaries between subjects would become apparent. At the same time students may learn how to use readily available resources, including other students and staff, to pursue problems from one discipline to another (for example by walking from the Philosophy Department to Physics or Life Sciences).

The check on the problem is in some ways the most fundamental criticism of all. This part of the course would indicate how a revised formulation of a problem may be decisive, how background theories can unconsciously direct how problems are identified and formulated, how fashions and fads (and funding) can dictate the directions of intellectual effort. It would lead to a study of the history of ideas, showing that problems have histories, that philosophical problems usually have their roots elsewhere, in science, or religion or in social and moral dilemmas, that powerful themes can leak from one discipline to another and preoccupations often run in parallel in more than one field.

The section on logic would call for study of both the formal and informal methods of argument. Formal logic concerns rules of inference and the way that logical steps can be used to draw out the consequences of an argument or of a scientific theory, perhaps for testing or for technological application. Informal logic encompasses the tricks of debate that may be used to cover up logical and factual defects in a position. Discourse by politicians, theologians, creation scientists and advertisers would furnish material for critical study.

All of this could lead to exploratory reading of the Great Philosophers, though preferably not until the students have a firm sense of their own interests and problems. In this mood they might be less deferential to the greats, more critical and at the same time more willing to learn. This would contrast with the traditional situation where the young student is confronted with soaring abstractions and profound arguments utterly unconnected with the historical background or the problem situations which agitated the titans of the past. The novice is completely overwhelmed (who am I to criticise the great?) or else clings to a critique provided by the teacher. The usual result is either a student who is indoctrinated into a system of thought, or else a person who is skilled in certain methods and techniques without any sense of purpose or perspective. No course can be rendered failsafe against authoritarian teachers, or against complete lack of interest on the part of students but the approach sketched above would provide interested people with a chance to avoid the more obvious dead ends of contemporary philosophy, and to apply imaginative criticism to their own professional and personal concerns.