This fallacy site defines this fallacy as simply: "The appeal to pity takes place when an arguer tries to get people to accept a conclusion by making them feel sorry for someone."
Classic example: The boy who killed his parents pleads for mercy from the judge on the grounds of being an orphan.
Of course, pity is just one of the emotions which can be manipulated in order to attempt to overwhelm reason and to score points.
While a member of Congress from his home state of Tennessee, Davy Crockett is believed to have given a successful speech refuting an appeal to pity, regarding a Congressional appropriation of money to a widow:
"Mr. Speaker -- I have as much respect for the memory of the deceased, and as much sympathy for the sufferings of the living, if suffering there be, as any man in this House, but we must not permit our respect for the dead or our sympathy for a part of the living to lead us into an act of injustice to the balance of the living. I will not go into an argument to prove that Congress has no power to appropriate this money as an act of charity. Every member upon this floor knows it. We have the right, as individuals, to give away as much of our own money as we please in charity; but as members of Congress we have no right so to appropriate a dollar of the public money. Some eloquent appeals have been made to us upon the ground that it is a debt due the deceased. Mr. Speaker, the deceased lived long after the close of the war; he was in office to the day of his death, and I have never heard that the Government was in arrears to him. This Government can owe no debts but for services rendered, and at a stipulated price. If it is a debt, how much is it? Has it been audited, and the amount due ascertained? If it is a debt, this is not the place to present it for payment, or to have its merits examined. If it is a debt, we owe more than we can ever hope to pay, for we owe the widow of every soldier who fought in the war of 1812 precisely the same amount. There is a woman in my neighborhood, the widow of as gallant a man as ever shouldered a musket. He fell in battle. She is as good in every respect as this lady, and is as poor. She is earning her daily bread by her daily labor, and if I were to introduce a bill to appropriate five or ten thousand dollars for her benefit, I should be laughed at, and my bill would not get five votes in this House. There are thousands of widows in the country just such as the one I have spoken of; but we never hear of any of these large debts to them. Sir, this is no debt. The Government did not owe it to the deceased when he was alive; it could not contract it after he died. I do not wish to be rude, but I must be plain. Every man in this House knows it is not a debt. We cannot, without the grossest corruption, appropriate this money as the payment of a debt. We have not the semblance of authority to appropriate it as a charity. Mr. Speaker, I have said we have the right to give as much money of our own as we please. I am the poorest man on this floor. I cannot vote for this bill, but I will give one week's pay to the object, and if every member of Congress will do the same, it will amount to more than the bill asks."
That is one heck of a good argument - and an argument for the restraint of government as well. Crockett had the good sense to eliminate the tone of cold-hearted rationality with his offer at the end. More about the speech and its aftermath here.
Interesting fellow, Crockett. He was elected twice to Congress, then defeated twice, after which he said "I told the people of my district that I would serve them as faithfully as I had done; but if not ... you may all go to hell, and I will go to Texas."
Which he did, and was killed by the Mexican Army while defending the Alamo in 1836.
Image: David Crockett (1786-1836)
