If you call a tail a leg, how many legs has a dog? Five? No, calling a tail a leg don't make it a leg. - Abraham Lincoln
The quote is kind of right, but it was not said by Lincoln.
(and if he had said it, I imagine he would have used the proper doesn't...)
@Curt - who said it then? In the form I quoted, it's been commonly attributed to Lincoln. If it appeared elsewhere it's also more than possible Lincoln was borrowing the joke. He prided himself on being well read. It's also extremely likely he had read Uncle Tom's Cabin, since that was the book that generated most of the popular support and rhetoric for the American Civil War.
Also don't be too sure he didn't use the word 'don't' in that context. Modern American English usage is often very different from forms that were popular in the late 1800s.
And even the best educated US politicians frequently resort to using rustic and 'folksy' terms when they want to show they're "jus' plain folks like everybody else." The late Sen. Sam Erwin was a master at using an overdone Carolinian drawl while referring to himself as a "just simple country lawyer." The fact he was a Harvard Law School graduate didn't seem to hurt his 'down home' image one bit with his constituents.
If you get a chance, check out how George W. Bush's language and accent used to get more 'folksy' and 'Lone Star' when he was delivering a speech down south or out west as opposed to when he was speaking in Washington DC or in the mid-Atlantic and New England states. Especially cute was how the word America got pronounced as "America" , "A'merica" or even "Ah-MURK-ah" depending on who he was addressing.
Gotta love our politicos.