A radical is one who recommends fundamental reform. Since change of an essential sort can be effected by those who stand on either the right or the left of the political spectrum, radicalism is a diverse calling, descriptive of very different doctrinal positions indeed. However far apart we think these endpoints might be, they also possess certain characteristics in common. In this respect the left/right continuum is not linear, but circular, the extremes bending back like a key-ring to where they lie parallel, though still of course separate and opposed.