further overtures for a while; the other boys chattered among
themselves, about football and tennis, and Irving sat silent at the head
of the table. At last, however, Westby turned to him.

“Mr. Upton,” said Westby deferentially, “how would you explain this?
There’s a dog, and he must be doing one of two things; either he’s
running or he’s not running. If he’s not doing the one, he is doing the
other, isn’t he?”

“I suppose so,” said Irving.

“Well, he’s not running. Therefore—he is running. How do you explain
that, Mr. Upton?”

Irving smiled feebly; the other boys were thinking it over with puzzled
faces.

“That’s an old quibble,” said Irving. “The alternative for running is
not running. Therefore when he’s not running—he’s _not_ running.”

“I don’t see that that explains it,” answered Westby. “That’s just
making a statement—but it isn’t logic.”

“He’s not running is the negative of he’s running; he’s not not-running
is the negative of he’s not running—”

“Then,” said Westby, “how fast must a dog travel that is not not-running
to catch a dog that is not exactly running but only perhaps?”

The boys laughed; Irving retorted, “That’s a problem that you might work