When Mr. White makes his first wish he does not have much faith in the power of the monkey's paw. He did, however, pay Sergeant-Major Morris a small sum of money for it, so he must have some small credence. He makes a wish for two hundred pounds at the suggestion of his son Herbert. His first wish is modest because he wants to test the paw. The fact that he makes such a modest wish shows that he does not have much faith in the thing. He is aghast at the outcome. His modest wish for two hundred pounds is apparently granted, but at the cost of his son's horrible death at the textile mill.
Mr. White has no desire to make another wish. He is afraid of the monkey's paw because of the consequences of his first wish. But at his wife's insistence he wishes for his son to return to them. Now he is hoping against hope that the paw has no real power and that his wish will not come true. After all, the idea of a shriveled paw possessing any power to grant any kind of wish is fantastic. He tries to make himself believe it must have been a pure coincidence that he received two hundred pounds as compensation for his son's fatal accident.
When Mr. and Mrs. White hear the knocking at their door, both of them feel sure that it is Herbert who has returned to them from the dead. But only Herbert's mother wants to let him in. Herbert's father doesn't want to have to look at his son, who must be a monster. Mr. White had previously told his wife, when she forced him to make his second wish:
"He has been dead ten days, and besides he--I would not tell you else, but--I could only recognize him by his clothing. If he was too terrible for you to see then, how now?"
By the time he makes his third wish, Mr. White loathes the monkey's paw but believes completely in its supernatural power. He uses it to cancel out his second wish, so to speak, and seems to succeed in causing the person outside to stop knocking and go away. The paw has now lost its power, if it ever had any, because the Indian fakir had only specified three wishes for three owners, and Mr. White was the last owner. So there would be no way of testing the paw further.
The reader is left to wonder whether that was really Herbert knocking at the door or some stranger who finally gave up and went away just as Mr. White was making his final wish.