At the end of "The Monkey's Paw," what does the father understand that the mother does not?

Your question relates to the lesson of the story and the
huge gap of understanding that makes its ending so tragic. Let us cast our minds back to
the first introduction of the monkey's paw into the story, and the reason it was
created. Sergeant Major Morris, when showing the paw to the mesmerised Whites, tells
them that "it had a spell put on it by an old fakir" to show the importance of
fate:

He
wanted to show that fate ruled people's lives, and that those who interfered with it did
so to their sorrow.

What Mr.
White learns after making his second wish and then hearing the terrible thumping on the
door of his son's resurrected body, is that he is trying to meddle in his fate, which
will end in tragedy. The way in which the interminable knocking continues suggests that
what is outside the door wanting access is some sort of reanimated corpse, terrible in
death. Mr. White realises that meddling with fate further can only bring yet greater
tragedy and sadness upon them, and so wisely uses his third wish to counteract the
effects of the second, sending his son back to the grave. It is clear, however, that his
wife has not gained this understanding:

readability="9">

He heard the chair drawn back and the door
opened. A cold wind rushed up the staircase, and a long loud wail of disappointment and
misery from his wife gave him courage to run down to her side, and then to the gate
beyond.

Mr. White, it is
clear, learns his lesson, wheras his wife definitely does not, and cannot accept the
danger inherent in trying to influence or change our fate.