Having worked with veterans of the Vietnam War who had suffered severe brain damage, Howard Gardner noticed that the extent of their injuries was sometimes limited to very specific brain functions. Recent developments in neuroscience also suggest that there is a highly differentiated and modular structure to the brain. This would appear to be inconsistent with a unitary form of intelligence.

Gardner also considered the behaviours of autistic savants, prodigies and others who exhibit extremely well-developed abilities, often in quite specific domains and independently of their general ability. Dustin Hoffman's portrayal of the Rainman, based on a composite of real-life characters, is a classic example of the type.

This led Gardner to ask two fundamental questions. How did the human mind and brain evolve over millions of years? How can we account for the diversity of skills and capacities that are or have been valued in different communities around the world?

Until now, writes Gardner, the term intelligence has been limited largely to certain kinds of problem-solving involving language and logic. However, human beings are able to deal with numerous kinds of content besides words, numbers and logical relations - for example, space, music and the psyches of other human beings. Gardner proposed that definitions of intelligence need to be expanded to include human skill in dealing with these diverse contents.

According to Howard Gardner, human intelligence:

• comprises a set of skills that enable a person to resolve genuine problems encountered in life;

• is the ability to create an effective product or offer a service that is valued in a culture;

• has the potential for recognising or creating problems, thereby establishing the necessity for new knowledge.

Gardner further suggested a list of eight criteria which would enable the identification of distinct intelligences but stipulated that individual intelligences might not meet all of the criteria, which are to be considered indicative rather than prescriptive.

Gardner propounds that we all possess all eight intelligences. Of course, owing to the accidents of heredity, environment, and their interactions, no two of us will exhibit the same intelligences in precisely the same proportions. Our differing profiles of intelligence provide intriguing challenges and opportunities for those involved in education. Historically, most education systems have ignored these differences or, rather, they have adopted a simplified system of assessment. Such assessment may have resulted in a single numerical value - or have focused on a limited range of broadly similar skills. However, Gardner's model, with its eight different categories of cognitive skills, provides a more holistic view of an individual's capacity for learning. If we are prepared to utilise this new model, it provides us with the opportunity to fashion individualised programmes of learning that focus specifically on the particular strengths and thinking preferences of the individuals concerned.

The problem that now presents itself is how to assess the eight intelligences. Most of the activities that we undertake involve not a single intelligence working independently but a number of intelligences working in concert. For example, it would be easy (but wrong) to assume that doing maths involved the logical-mathematical intelligence exclusively. This would ignore the visual element that is entailed in geometry and trigonometry - and is also an important element in solving problems in algebra. It also ignores the fact that problems may be presented linguistically - and overlooks the fact that some mathematical problems can be re-interpreted so that they become more accessible to solution using different intelligences.

Over and above the difficulty of assessing intelligences that are not easily separated from one another is the question whether it is possible to isolate and measure raw intelligence at all. Even if it were possible to devise means of assessing intelligence levels, would these not be, at best, measures of developed intelligence and thereby dependent on the opportunity afforded individuals to develop that particular area of expertise?

Furthermore, we need to ask whether it is possible to compare measures of different kinds of intelligence? Surely, the way one assesses musical intelligence (for example) will be so different from the way one assesses interpersonal intelligence that it would be absurd to attempt a comparison.

Perhaps the real potential of Multiple Intelligences profiling will only be realised when we recognise that the process is not one of assessment (carried out for the benefit of educators) but rather of developing self-awareness in learners. When every individual learner is aware of their preferred means of processing and manipulating information, and is able to take ownership of the process, then we will begin to see the potential afforded by Gardner's theory of Multiple Intelligences.

Howard Gardner is Professor in Cognition and Education at the Harvard Graduate School of Education. He is also Adjunct Professor of Psychology at Harvard University, Adjunct Professor of Neurology at the Boston University School of Medicine, and Co-Director of Project Zero.

1. Potential isolation by brain damage

2. The existence of savants, prodigies and other exceptional individuals

3. An identifiable set of core operations

4. A distinctive developmental history - along with a definable set of expert 'end-state' performances

5. An evolutionary history and evolutionary plausibility

6. Support from experimental psychological tasks

7. Support from psychometric findings

8. Susceptibility to encoding in a symbol system

The original exposition of the theory of Multiple Intelligences, this is not always an easy read - but well worth the effort for anyone who seriously wants to get to grips with this revised framework for understanding the nature of intelligence. Gardner draws upon a vast resource of background knowledge, as well as on his own research, as he explains the derivation of the theory and expands upon the nature of each of the intelligences. Extensive footnotes (thoughtfully located at the back of the book, away from the main text) provide useful starting points for further study.