“But what is reality?” asked the gnomelike man. He gestured at the tall banks of buildings that loomed around Central Park, with their countless windows glowing like the cave fires of a city of Cro-Magnon people. “All is dream, all is illusion; I am your vision as you are mine.”Dan Burke, struggling for clarity of thought through the fumes of liquor, stared without comprehension at the tiny figure of his companion. He began to regret the impulse that had driven him to leave the party to seek fresh air in the park, and to fall by chance into the company of this diminutive old madman. But he had needed escape; this was one party too many, and not even the presence of Claire with her trim ankles could hold him there. He felt an angry desire to go home—not to his hotel, but home to Chicago and to the comparative peace of the Board of Trade. But he was leaving tomorrow anyway.“You drink,” said the elfin, bearded face, “to make real a dream. Is it not so? Either to dream that what you seek is yours, or else to dream that what you hate is conquered. You drink to escape reality, and the irony is that even reality is a dream.”“Cracked!” thought Dan again.“Or so,” concluded the other, “says the philosopher Berkeley.”“Berkeley?” echoed Dan. His head was clearing; memories of a Sophomore course in Elementary Philosophy drifted back. “Bishop Berkeley, eh?”“You know him, then? The philosopher of Idealism—no?—the one who argues that we do not see, feel, hear, taste the object, but that we have only the sensation of seeing, feeling, hearing, tasting.”“I—sort of recall it.”“Hah! But sensations are mental phenomena. They exist in our minds. How, then, do we know that the objects themselves do not exist only in our minds?” He waved again at the light-flecked buildings. “You do not see that wall of masonry; you perceive only a sensation, a feeling of sight. The rest you interpret.”“You see the same thing,” retorted Dan...