"There are," the robot said rather wearily, "only a limited number of character matrices possible, depending first on the arrangement of the genes within the chromosomes, and later upon environmental additions. Since environments tend to repeat--like societies, you know--an organizational pattern isn't hard to lay out, along the Kaldekooz time-scale. You follow me so far?" "By the Kaldekooz time-scale, yes," Martin said. "I was always lucid," the robot remarked a little vainly, nourishing a swirl of red ribbon. "Keep that thing away from me," Martin complained. "Drunk I may be, but I have no intention of sticking my neck out that far." "Of course you'll do it," the robot said firmly. "Nobody's ever refused yet. And don't bicker with me or you'll get me confused and I'll have to take another jolt of voltage. Then there's no telling how confused I'll be. My memory gives me enough trouble when I temporalize. Time-travel always raises the synaptic delay threshold, but the trouble is it's so variable. That's why I got you mixed up with Ivan at first. But I don't visit him till after I've seen you--I'm running the test chronologically, and nineteen-fifty-two comes before fifteen-seventy, of course." "It doesn't," Martin said, tilting the glass to his lips. "Not even in Hollywood does nineteen-fifty-two come before fifteen-seventy." "I'm using the Kaldekooz time-scale," the robot explained. "But really only for convenience. Now do you want the ideal ecological differential or don't you? Because--" Here he flourished the red ribbon again, peered into the helmet, looked narrowly at Martin, and shook his head. "I'm sorry," the robot said. "I'm afraid this won't work. Your head's too small. Not enough brain-room, I suppose. This helmet's for an eight and a half head, and yours is much too--" "My head _is_ eight and a half," Martin protested with dignity. "Can't be," the robot said cunningly. "If it were, the helmet would fit, and it doesn't. Too big." "It does fit," Martin said. "That's the trouble with arguing with pre-robot species," ENIAC said, as to himself. "Low, brutish, unreasoning. No wonder, when their heads are so small. Now Mr. Martin--" He spoke as though to a small, stupid, stubborn child. "Try to understand. This helmet's size eight and a half. Your head is unfortunately so very small that the helmet wouldn't fit--" "Blast it!" cried the infuriated Martin, caution quite lost between Scotch and annoyance. "It does fit! Look here!" Recklessly he snatched the helmet and clapped it firmly on his head. "It fits perfectly!"