Thinking skills are all the rage, although there are concerns about how to assess them. One of the best-known approaches is CASE, the Cognitive Acceleration through Science Education project, which Professor Phil Adey and his colleagues at King’s College, London have devised over the past 20 years. The CASE programme consists of a set of activities designed to be used once every couple of weeks during the early years of secondary school.

Here, though, I want to suggest something more modest - a single activity to help pupils at key stage 3 or 4 think about what science is and how it is done. The activity also introduces them to some of the thinking within post-modernism. (Post-modernism is an intellectual discipline that has grown in significance over the past 20 years. It is suspicious of the modernist belief that there is such a thing as “absolute objectivity”. It is intended to get pupils to think about science and to appreciate that there is no one single way of being a scientist.) I have written this account of the activity with the biology element as the strongest - but it can easily be adapted if you would rather the emphasis is on chemistry or physics.

The activity would be best done in a wood. However, if you have not got a wood, do it on grassland (for example in the school grounds) and substitute “rabbits” for “grey squirrels”. Of course, you can do the whole activity in a classroom, though it will be less memorable and probably more difficult for some pupils to appreciate what the activity is driving at.

Get your pupils to stand (or imagine they are standing) in a wood (or grassland) and then think of the ways in which a scientist might study it. Depending on your pupils you may be able simply to get them to talk about this in pairs or small groups for five minutes, or you may have to help them a bit. The point is that there are many ways in which scientists can and do study woods. For a start, a biologist would be most interested in the organisms in the wood, a climatologist would study such things as sunshine, rainfall and wind and a geologist would focus on the underlying rocks and the consequences of these for the soil.

There are a great variety of ways in which just the biologists might work in a wood. There are the obvious niche-specific roles occupied by those who define themselves as microbiologists, botanists, mycologists (who study fungi) and zoologists. In addition, the wood will be full of ecologists, anatomists, biochemists, physiologists and even such difficult-to-classify creatures as Oliver Rackham, interested in the history of the wood as revealed by a variety of different approaches including field archaeology, the study of place names and dating trees by their rings.

We can subdivide further. Our ecologists will include population biologists (counting the numbers of individuals within species and organising these individuals in terms of how old they are), ecological geneticists (concerned with relationships between DNA sequences and fitness), autecologists (each occupied with the ecology of a single species), synecologists (attempting to unravel the interrelationships between species), conservation biologists (concerned to prevent, through careful management, the loss of species from the wood) and so on.

In addition to the large number of scientists now found investigating every aspect of this overcrowded wood, many other types of scientists exist, though they are unlikely to be found studying woods or, which is perhaps more important, using the methods of biologists, climatologists and geologists. An analytical chemist, a theoretical physicist, a palaeontologist and a professor of cardiac surgery have little in common from a methodological standpoint. Attempts to produce a list of what unifies such a disparate group of people tend to end up generating criteria that include geographers, historians, economists, philosophers and just about any one who seeks after testable truth. There is no such thing as “the scientific method” - even though KS3 and GCSE science all too often give the impression that there is.

Your average pupil may agree that there are a wide variety of both scientific approaches (crudely, the “processes” of science) and scientific domains (crudely, the “contents” of the various sciences) but will still assume the existence of one actual reality. This fairly conventional view would entail believing that the universe (more formally, that large part of it susceptible to scientific enquiry) is so rich that no single scientific way of exploring it suffices; instead a variety of approaches are needed, with these approaches being situated within relatively distinct (albeit it overlapping) domains. In other words, there is a biology of a wood, a chemistry of a wood, a geology of a wood and so on, but there is just the one wood being studied!

A more radical view, informed by post-modernism, cheerfully asserts that the wood being studied, while undoubtedly a single wood in everyday language, actually exists - or, at the very least, reveals itself - differently to different investigators. I will not rely on this more radical view but some pupils may be intellectually attracted by it. To many, it may seem an absurd view but it may be easier to see its force if we imagine not a whole wood but a single species, say the grey squirrel, in the wood being studied. I need not rehearse again in any detail the various biological approaches to studying grey squirrels - anatomical, biochemical, physiological, behavioural and so on. But consider just the behavioural approach.

At one extreme, imagine how such behaviourists as Pavlov (of Pavlov’s dogs) and Skinner (designer of the Skinner box, in which the learning of rats, pigeons and other animals can be quantitatively investigated) might proceed. They would probably obtain a number of grey squirrels and keep them in isolation in carefully controlled laboratory settings. Here individual squirrels would be tested to see which particular features of the environment allowed effective learning to take place. For example, do squirrels innately prefer certain materials from which to fashion a drey (nest)? How long do they take to learn which foods are edible and which are not? And so on.

At the other extreme, imagine how the pioneer of long-term fieldwork on chimpanzees in their natural setting, Jane Goodhall, might proceed. She would probably spend many months accustoming the squirrels to herself, and herself to their habitat. Gradually she would begin to notice patterns in their behaviours and to see the various squirrels as individuals. Undoubtedly she would give her study animals their own names, see signs of differences in personality and behaviour and begin to appreciate how they relate to one another.

These two different approaches to studying the behaviour of squirrels, one experimental and interventionist, the other ethnographic and naturalistic, evidently reveal different understandings of what it is to be a grey squirrel. But in a sense each approach brings into existence a different kind of grey squirrel. It might be objected that this is ridiculous. After all, grey squirrels will carry on doing whatever they do irrespective of the relative extent to which they are studied by these two approachs or any others. However, even granted the truth of this assertion - an assertion which arguably belongs more to the realm of metaphysics than to that of science - it is certainly the case that what you or I think of as a grey squirrel is not just affected but determined by a blend of who each of us is and how squirrels have been studied and reported. After all, in the UK are grey squirrels vermin that should be exterminated, a valuable source of food and pelts or a much loved animal and one of the few British wild mammals people actually see in the countryside?

Finally, pupils can think about two things. First, the diversity of ways of investigating other questions in science. For example, how can scientists study the effects of rising atmospheric carbon- dioxide levels (for example, look at the consequences for climate and on organisms, carry out controlled experiments in laboratories where carbon-dioxide levels can be changed, run computer simulations, devise and explore theoretical models using physics and atmospheric chemistry). Second, they can think about the limitations of science. After all, science will not tell us whether we should do anything to cut carbon-dioxide emissions or, if we agree that we should, how countries should deal with nations that refuse to do their bit.

Michael J Reiss is professor of science education at the University of London Institute of Education. This article is based on his inaugural lecture ‘Representing Science’ (Institute of Education, pound;3. Tel: 020 7612 6050. E-mail bmbc@ioe.ac.uk)