"The story which introduces Professor S. F. X. van Dusen, professional scientific supergenius, who lends his talents to solving baffling mysteries. He is described as primarily a logician, who spent years proving that 2+2=4, except in the rare cases when it doesn't."

It was a beautifully clever story, although it featured on its own very little math. However, I'm glad it's archived here anyway, since it was a *pleasure* to read.