Is beauty objective or subjective? That is, is it a quality of the objects we find beautiful, perhaps inhering in symmetry, the golden mean and other such 'perfect' proportions or form; or is it in the eye (or mind) of the beholder, a matter of personal response? Our intuitions tend to be divided on this question, and partly for this reason it is a longstanding and difficult problem for aesthetics. One possible solution was developed by the Enlightenment philosopher, Immanuel Kant. Kant's position was basically this: beauty is indeed a subjective response, but it is one which we can all expect to share. The reason for this, according to Kant, is that our minds are constituted in the same way, and so, faced with the same object we are capable of having the same perceptions of beauty that others have. So, if beauty is not quite an objective feature of the world, it is an objective feature of human perception of the world.

This has always seemed an appealing idea to me. The trouble with it is that Kant fleshed it out in terms of his particular idealist account of the mind. From a twenty-first century perspective, metaphysical idealism of any stripe is suspect – we prefer to have things explained in terms of physical causes rather than metaphysical principles, and matters of the mind, now that we know much more about the physical workings of the brain, are no exception. But this, says Jennifer A. McMahon in her book Aesthetics and Material Beauty: Aesthetics Naturalized, should not put us off Kant's general approach. She claims that his basic insight can be preserved, while replacing his idealism with an up-to-date physicalism, that sees perception and cognition as governed by natural, physical processes.

McMahon is a professional philosopher and this is a work of professional philosophy, so the lay reader should be warned that parts of it are tough going. Her thesis, however, is one that anyone with an open-minded concern in the arts is likely to be interested in. McMahon's approach, it should be said, is vastly more sophisticated than that of neurophysiologists who have identified beauty with mechanisms such as the 'peak-shift' effect. On this account, certain kinds of stimuli prompt a proportional response, so that the engineering of a 'super-stimulus' – out of proportion with anything found in nature, prompts a 'super-response'. Think of this as the Pamela Anderson theory of beauty. McMahon is too attentive to the complexities of the experience of beauty to countenance that idea. Beauty, she acknowledges, while always a pleasurable experience, is also tied up with various other experiences, of harmony, delicacy or vitality, and so on. She also acknowledges that it involves not only feeling, but understanding. It 'turns our attention to our integration into something beyond ourselves' – the natural world, in the case of naturally occurring beauty, and in the case of art and artefacts, a 'community of minds'.

The basic outlines of McMahon's theory are as follows. In ordinary visual perception, the visual system – the eyes and parts of the brain concerned with visual processing – extract information required to build up an accurate mental representation of our environment. Different interconnected modules within the visual system register different features – edges, texture, tonal gradation, colour, and so on. However, these modules do not always give consistent information, so that in order for visual perception to work some are given more priority in object recognition. While most of this occurs unconsciously and automatically, prioritisation may be acculturated, and even consciously influenced, as when we switch between interpretations of an ambiguous image, such as the duck–rabbit figure. McMahon suggests that in some cases of perception, rather than requiring one or other module to be prioritised, modules give consistent information, functioning in 'equilibrium' or 'harmonious combination'. In such cases we find the perceived object beautiful. We are especially apt to find nature beautiful because our visual system has evolved in order to efficiently process its forms: 'We could say that the structures that constitute perception recognize their parents in certain natural forms; that is, the very kinds of form that were responsible for the way they had evolved in the first place. Such forms, presumably economically structured trees, hills, plains and so on, are experienced – unless we are conditioned otherwise – as perfectly attuned to our perceptual apparatus'. Visual artists with an eye for beauty can achieve a similar effect, contriving their forms to 'achieve some sense of rapprochement' between modules that ordinarily give conflicting input.

While the book's focus is on developing this account, other chapters see McMahon address ugliness, present an ontology of art, and explain a quality of pictures she calls 'realism', by which she means not verisimilitude, but the sense of 'truth' or 'rightness' of a particular style. Given our still incomplete understanding of the operations of the brain and mind, it is only to be expected that McMahon puts much of this tentatively. Nevertheless, she says enough to persuade me that her 'naturalising' approach – explaining phenomena in terms of physical structures and principles – yields substantial dividends in the case of beauty, one of the very toughest chestnuts in aesthetics.

The one complaint I have is with McMahon's account of what art is – her ontology of art. For McMahon, art must be aesthetic. That means that it must be, for the most part, beautiful. So, while she gives a sensitive analysis of the achievements of a range of modern and postmodern artists, from the Analytical Cubism of Picasso and Braque, to Duchamp, Magritte, Damien Hirst and Patricia Piccinini, she often dismisses their work as non-art: 'I do not engage with Duchamp's urinal as art. I engage with it as a treatise on art'. This exclusive notion of art seems to me just wrong. I would rather have a pluralistic account where beauty is only one value of many that can contribute to some thing's status as art. But this complaint does nothing to impugn McMahon's powerful and original account of beauty. And in any case, if loving beauty too much is a fault, well, it is not an unattractive one.