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Eric Laithwaite's review of my book, The Mangle of Practice: Time, Agency, and Science (THES, June 21), makes little attempt to discharge the first duty of a reviewer, namely to give readers some idea of what the book under review is about. Instead his review consists mainly of anecdotes and sarcastic remarks about sociology as a discipline, and about me.

The closest he gets to the substance of the book is to quote a few randomly chosen sentences, where he makes an important and systematic error: he substitutes "ageing" three times for agency. "Agency" is central to the book, which discusses how the practices of scientists ("human agency") intertwine with the performances of instruments and machines ("material agency") in the production of knowledge - it is not a book about getting old.

Andrew Pickering Department of sociology University of Illinois at Urbana-Champaign