A freshman college student asked his grade advisor what he should study. "Logic," was the answer.
"What is logic?"
"Logic enables one to deduce certain facts from others. For example, do you have a lawn mower?"
"Yes."
"From which I conclude that you have a lawn."
"Yes, I have a lawn."
"From which, I take it, you have a house."
"Yes, I have a house."
"Then you are married."
"Yes, I have a wife."
"And children?"
"Yes, I have children."
"From which I conclude that you are a heterosexual male."
"I am indeed a heterosexual male. Gee, this logic is amazing! From the fact that I have a lawn mower, you could deduce that I am an heterosexual male. Remarkable!"
As would happen, later the student met in the hall another student whom he knew and told him that he should study logic.
"What is that?" the friend asked.
"It enables you to deduce one proposition from another. For example, do you have a lawn mower?"
The friend replied, "No." The student then said, "You faggot!"