d 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
out on the blackboard sometime."

Thereupon Westby became silent, and Irving more than half repented of
his speech; he knew that in its reference it had been ill-natured.

He noticed later in the day when he went up to the dormitory that the
boys tiptoed about the corridors and conversed in whispers; there was an
extravagant air of quiet. When they went down to supper, they tiptoed
past Irving's room in single file, saying in unison, "Sh! Sh! Sh!" They
all joined in this procession--from Collingwood to Allison. Irving felt
that he had taken Allison's place as the laughing-stock, the butt of the
dormitory.

In the evening they came to bid him good-night--not straggling up as they
usually did, but in a delegation, expectant and amused. Westby and
Collingwood were in the van when Irving opened his door in response to
the knock.

"We didn't know whether you'd shake hands with two such reprobates or
not," said Westby. "We thought it wasn't quite safe to come up alone--so
we've brought a bodyguard."

Irving did not smile, though, all the boys were grinning. He shook hands
formally with Collingwood, then with Westby, then with the others,
saying good-night to each; as they left him, they tiptoed to their
rooms. He thought grimly that, whatever might be the sentiments
entertained towards him, he would not long be living in an atmosphere of
ridicule.

Irving had charge of the "big study," as it was called, during the hour
immediately after morning chapel. The boys filed in from chape