Hardy's writing often explores what he called the "ache of modernism", and this theme is notable in Tess, which, as one critic noted, portrays "the energy of traditional ways and the strength of the forces that are destroying them". In depicting this theme Hardy uses imagery associated with hell when describing modern farm machinery, as well as suggesting the effete nature of city life as the milk sent there must be watered down because townspeople cannot stomach whole milk. Angel's middle-class fastidiousness makes him reject Tess, a woman whom Hardy presents as a sort of Wessex Eve, in harmony with the natural world. When he parts from her and goes to Brazil, the handsome young man gets so ill that he is reduced to a "mere yellow skeleton". All these instances have been interpreted as indications of the negative consequences of humanity's separation from nature, both in the creation of destructive machinery and in the inability to rejoice in pure and unadulterated nature.
On the other hand, Marxist critic Raymond Williams in The English Novel From Dickens to Lawrence questions the identification of Tess with a peasantry destroyed by industrialisation. Williams sees Tess not as a peasant, but as an educated member of the rural working class, who suffers a tragedy through being thwarted, in her aspirations to socially rise and her desire for a good life (which includes love and sex), not by industrialism, but by the landed bourgeoisie (Alec), liberal idealism (Angel) and Christian moralism in her family's village (see Chapter LI).
Another important theme of the novel is the sexual double standard to which Tess falls victim; despite being, in Hardy's view, a truly good woman, she is despised by society after losing her virginity before marriage. Hardy plays the role of Tess's only true friend and advocate, pointedly subtitling the book "a pure woman faithfully presented" and prefacing it with Shakespeare's words from The Two Gentlemen of Verona: "Poor wounded name! My bosom as a bed/Shall lodge thee." However, although Hardy clearly means to criticise Victorian notions of female purity, the double standard also makes the heroine's tragedy possible, and thus serves as a mechanism of Tess's broader fate. Hardy variously hints that Tess must suffer either to atone for the misdeeds of her ancestors, or to provide temporary amusement for the gods, or because she possesses some small but lethal character flaw inherited from her ancestors.
Because of the numerous pagan and neo-Biblical references made about her, Tess has been viewed variously as an Earth goddess or as a sacrificial victim. For example, early in the novel, she participates in a festival for Ceres, the goddess of the harvest, and when she baptises her dead child she chooses a passage from Genesis, the book of creation, rather than the more traditional New Testament verses. Then at the end, when Tess and Angel come to Stonehenge, which was commonly believed in Hardy's time to be a pagan temple, she willingly lies down on a stone supposedly associated with human sacrifice.
Tess has also been seen as a personification of nature and her association with animals throughout the novel emphasizes this idea. Tess's misfortunes begin when she falls asleep while driving Prince to market, and causes the horse's death; at Trantridge, she becomes a poultry-keeper; she and Angel fall in love amid cows in the fertile Froom valley; and on the road to Flintcombe-Ashe, she kills some wounded pheasants to end their suffering.
However, Tess emerges as a powerful character not because of this symbolism but because "Hardy's feelings for her were strong, perhaps stronger than for any of his other invented personages".
Hardy, 16 years old at the time, saw the hanging of Elizabeth Martha Brown, who murdered her violent husband. This experience, which fascinated and repelled Hardy, contributed to the writing of Tess.