Sondheim on what makes a good critic

For me, a good critic is a good writer. A good critic is someone who recognises and acknowledges the artist's intentions and the work's aspirations, and judges the work by them, not by what his own objectives would have been. A good critic is so impassioned about his subject that he can persuade you to attend something you'd never have imagined going to. A good critic is an entertaining read. A good critic is hard to find.

--  Stephen Sondheim, from Look, I Made a Hat (Virgin Books, 2011)

And see:

Stephen Sondheim: who needs critics?
Good reviews can be as harmful as bad ones, says Stephen Sondheim. In an extract from his new book, he reflects on a life of prizes, putdowns – and the joy of songs sung in Sanskrit
The Guardian, November 20, 2011