chapter 6 Explain the statement made by Justice Wargrave about Providence.` `
Wargrave's statement about providence can be understood on multiple levels. On the most basic level, it represents a rejoinder to Miss Brent's assertion that Mrs. Rogers' death was an act of God. On a deeper level, however, with the revelation that Wargrave himself was the murderer, these words provide insight into his own mindset and motive. Wargrave selects people that the legal system has failed to bring to justice, thus taking retribution into his own hands through violence.
By this point, early in chapter 6, Mrs. Rogers has become the second person to die on the island. In response, Miss Brent declares this death to have been an act of God, stating:
You regard it as impossible that a sinner should be struck down by God! I do not!
It is in response to this statement that Wargrave makes his comment about providence:
My dear lady, in my experience of ill-doing, Providence leaves the conviction and chastisement to us mortals -- and the process is often fraught with difficulties. There are no short cuts.
In essence, Wargrave is telling Brent that there is no such thing as divine retribution, but that any form of retribution is only ever dealt by human beings. These words serve to counter Brent's earlier thoughts on the matter.
However, at the same time, there is a deeper meaning to Wargrave's words (beyond them having been a rejoinder to Brent's assertion). Remember, Agatha Christie reveals at the book's end that it was Wargrave himself who was the murderer (an important note which adds additional levels of nuance to this particular statement).
As his confession clarifies (at the end of the book), Wargrave possesses an internal tension between his strict legalism and the sadistic and murderous tendencies he'd long held in check. It is this internal tension that, at the end of his life, unleashes Wargrave's murder-plot. Seen within this context, these words actually allude to Wargrave's own motive for the murders. He has chosen for his victims those who the legal system itself has been unable to bring to justice and has chosen to take retribution into his own hands. If the legal system has failed, his reasoning assumes, and there is no providence to rely upon, then it falls upon human beings to take retribution for themselves. In the process, he is also given the ability to finally indulge the murderous impulses he has long suppressed.
Thus, on one level, these words represent a rejoinder taken within the context of a conversation, and an assertion that Mrs. Roger's murder was an act of human culpability rather than one of supernatural explanation. On a more fundamental level, it can be understood as a piece of foreshadowing to the murderer's identity, providing a window into his mindset.