Clare merely has the appearance of a working man, just as Tess merely has the appearance of a maiden in white: "His aspect was probably as un-Sabbatarian a one as a dogmatic parson's son often presented; his attire being his dairy clothes, long wading boots, a cabbage-leaf inside his hat to keep his head cool, with a thistle-spud to finish him off"(Chapter 23). But the surface appearance of change, either of clothing for Clare, or temporarily of location for Tess cannot fundamentally change society. Tess ends as she began -- in a primitive ritual, covered with the blood of Alec, the man who destroyed her life and chastity, before Stonehenge. And she is accompanied by a man who also destroyed...

One man ignored conventional morality, or obeyed the conventional morality that said a lord has a right to his servants. One man obeyed conventional morality by casting off an unchaste woman -- even though he tried to ignore such morals by marrying 'beneath himself.' But Hardy's subtitle that says Tess is a pure woman suggests that only the morality of the ancients speak the truth, and transcend the limits of the common spirit endemic to rural England.
Works Cited

Hardy, Thomas. Tess of the d'Urbervilles: A pure woman.

Online literature. August 11, 2009.

http://www.online-literature.com/hardy/tess_urbervilles/