A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

A local United Way office realized that...
A local United Way office realized that it had never received a donation from the town's most successful lawyer. The person in charge of contributions called him to persuade him to contribute. "Our research shows that out of a yearly income of at least $500,000, you give not a penny to charity. Wouldn't you like to give back to the community in some way?" The lawyer mulled this over for a moment and replied, "First, did your research also show that my mother is dying after a long illness, and has medical bills that are several times her annual income?" Embarrassed, the United Way rep mumbled, "Um...no." "-or that my brother, a disabled veteran, is blind and confined to a wheelchair?" The stricken United Way rep began to stammer out an apology but was interrupted, "-or that my sister's husband died in a traffic accident," the lawyer's voice rising in indignation, "leaving her penniless with three children?" The humiliated United Way rep, completely beaten, said simply, "I had no idea..." On a roll, the lawyer cut him off once again: "-so if I don't give any money to them, why should I give any to you?"