Abstract
The category 'radicalism' can be used in two ways. If we are looking at usage, what historians have generally used the term to mean, then it must be a phenomenon that is strongly situational and without a core content that can give it substantive identity; if we stipulate a definition that enables more precise attributions of identity, we run the risk of talking about our words more than the words of people in the past, because we open ourselves to the endless multiplication of definitions, and endless (fruitless) argument about which is the 'right' one. I suspect the sceptics are right, and that we would be better to find words and categories that cut less across the grain of the seventeenth-century past; but I suspect just as strongly that any hope of doing without the category of radicalism is a forlorn one.