Philosophers have traditionally decried vagueness as an unmitigated evil, and natural scientists have consistently agreed with them. Nevertheless, as I hope to show, the vagueness of scientific terms has some important advantages for the theories in which these terms figure. In so arguing I do not mean to put the best face on some unpleasant facts or to make a virtue out of a necessity. I shall begin, however, by arguing that on some contemporary accounts of scientific language the vagueness (...) of many scientific terms is unavoidable; if it is unavoidable then lamenting it is futile, and justifying it is idle. I shall go on to argue that, independent of these accounts, the advantages of exactness attained can sometimes be substantially outweighed by the disadvantages of vagueness foregone. (shrink)