Though the concept was not fully worked out until Hardy's later poetic work on Napoleon, The Dynasts, Hardy came to believe early on, even before his days in London as an assistant architect, that events in human lives were not ordered by the will of man nor by the Providence of God but by the power of coincidence, accident, fate, bad luck and the forces of history. Published in 1891, Tess of the D'Urburvilles shows directly and indirectly this belief in what might be called the "omnipotent power of destiny or fate."
[Angel Clare] observed his own inconsistencies in dwelling upon accidents in Tess's life as if they were vital features.
This quote of the narrator's words is in reference to Clare's musing remonstrances of himself for hesitating to tell his parents more about Tess when he went to them for counsel on marrying. It indicates clearly how Hardy directly incorporates his belief in a controlling fate of accidental and coincidental circumstance intertwined with good or bad luck as Clare considers "the accidents" of Tess's life, though he as yet does not know the reality of the details of the worst of these accidents.
Some references to this principle of Hardy's, which he later called Immanent Will, are indirect; they are implied by character thoughts and statements or events or surroundings. An instance of this is when Tess is remonstrating with herself over being too diffident to write to Clare during their estrangement while he is in Brazil. She meets greater suffering and tragedy than she might have otherwise because of accidental consequences from not exerting herself sooner and more directly:
[Tess]: "I won't dally like this any longer! I have been very wrong and neglectful in leaving everything to be done by him."
Tess has delayed and thus by accidental neglect sets up the opportunities for greater troubles that lead to despair and the eventual abandonment of her good principles that might have (not surely, but perhaps) led her down a less fateful course.
It is through characterization such as this and through events surrounding them that Hardy incorporates his principle--which may be described as the "omnipotent power of destiny or fate"--that fate's luck, accidents, coincidences, and historical impetuses arbitrarily and mercilessly order the affairs of human lives.
No single reason is responsible for the tragedy in all his novels, "fate", "character", "society", "chance and coincidence" plays a crucial part in the tragedy of Hardy's novel. Different devices of tragedy is employed by Hardy in different novel. In "The Mayor of Casterbridge", "character" was responsible for the tragedy in the play. In "The return of the native", "chance and coincidence" played a greater role in bringing about tragedy. In "Tess of the D'Urbervilles", "fate" plays a considerable role to contribute to the tragedy of the novel.
Hardy personifies "fate" at the end of the novel, as the president of the immortals, reveals itself in two forms - "Nature and "chance and coincidence"- Nature plays a key role in the novel, it is always indifferent and hostile, and never a source of comfort and pleasure. When "Tess" was seduced, nature was indifferent, when "Tess" was in miserable condition, nature was more hostile by the rigours of winter at Flintcomb-Ash, "a starve-acre place".
"Chance and coincidence" also played a crucial role in the life of "Tess" and made it miserable. "Tess" seek employment at the D'Urberville house, by chance, chance was responsible to make her seduction by Alec possible, her letter of confession lips under the rug and does not reach Angel, by chance, she confronted Alec, once again in life by chance and so on.
Therefore "fate" both in the form of "nature" and "chance and coincidence" plays a crucial role in the life of "Tess" and contributed to the tragedy of the novel.