It was to be expected that, as one of the leading proponents of chaos and complexity theory in Britain, Ian Stewart (Letters, THES, January 5) would not take kindly to Geoff Mulgan's criticisms of the hype surrounding complexity theory (³ÉÈËVRÊÓƵ View, THES, December 22). But Stewart should at least have taken more care in reading what Mulgan is saying before putting pen to paper.

In the first place, Mulgan did not claim that chaos and complexity have "no useful applications".

Rather he said there have been "some successes in biology and physics", but nothing of much use in the social sciences - a point confirmed it seems to me by the rather meagre list of successes provided by Stewart.

Stewart wants to have his cake and eat it: playing the underdog, he says chaos and complexity suffer from the "Rolls-Royce problem" - like a new car up against a Rolls-Royce, they find it hard to gain recognition in the face of a well-established paradigm. But he concludes that the appeal of the new theories is the "manifest failure of the old ones".

³ÉÈËVRÊÓƵ

Hmm . . . I did not realise Rolls-Royce engines were such a failure! Contradictions aside, Stewart's conclusion confirms a point made by Gillot and Kumar (Science and the Retreat from Reason, 1995, Merlin Press) that enthusiasts for chaos and complexity employ a negative proof procedure - they trade on the failure of other theories rather than the virtues of their own.

Second, I took Mulgan's point about religion and complexity not to be that, as a technical discipline, complexity amounts to religion, but rather that in their popular writings, leading proponents of the theory incline to a mystical, teleological point of view.

³ÉÈËVRÊÓƵ

On my reading, there is a connection between the hype surrounding the theory and religious interpretations of it - the mystical interpretations follow from the claim that complexity amounts to a universal theory of nature.

My interpretation would be that a liking for these conclusions drives the claims to universality, rather than the reverse being the case.

God forbid that scientists be forbidden from expressing an opinion on the implications of their theories.

But if they do, they cannot complain when a critical sociological eye is cast over their claims.

³ÉÈËVRÊÓƵ

Stuart W. G. Derbyshire

Research fellow

University of Manchester Rheumatic Diseases Centre

Hope Hospital, Salford