"Cynics," the "dog philosophers" of the Greek and Roman world, so called almost certainly from the nickname of Diogenes of Sinope, were not a continuous school of theoretical philosophy but an erratic succession of individuals who from the fourth century BCE to the sixth century CE preached, through ascetic practice and mordant denunciation of established convention, a more or less similar way of life designed to lead to the happiness of the individual. Consequently there is no established doctrinal canon by which to define an "orthodox" Cynic, and the ancient but still lively debate as to whether Antisthenes or Diogenes was the founder of Cynicism is an unreal one. Nevertheless, despite marked variations of stress and tone in individual exponents, Diogenes was always regarded as the arch-Cynic, and a sufficient number of characteristic attitudes recur to identify the movement.

The nature of the existing evidence of Cynicism is...