Pollux said, "But, Dad, you can't load a ship if you don't know where it's going."

Castor glared at him; Roger Stone stared at him. "Oh," he said slowly, "I begin to see. But don't worry about it. As skipper, it is my responsibility to see that we have whatever we need aboard before we blast."

Dr. Stone said quietly, "Don't tease them, Roger."

"I'm not teasing."

"You're managing to tease me, Daddy," Meade said suddenly. "Let's settle it. I vote for Mars."

Hazel said, "The deuce it ain't!"

"Pipe down, Mother. Time was, when the senior male mem­ber of a family spoke, everybody did what he -"

"Roger, if you think I am going to roll over and play dead-"

"I said, "pipe down." But everybody in this family thinks it's funny to try to get around Pop. Meade sweet-talks me. The twins fast-talk me. Buster yells until he gets what he wants. Hazel bullies me and pulls seniority." He looked at his wife. "You, too, Edith. You give in until you get your own way."

"Yes, dear."

"See what I mean? You all think papa is a schnook. But I'm not. I've got a soft head, a pliable nature, and probably the lowest I.Q. in the family, but this clambake is going to be run to suit me."

"What's a clambake?" Lowell wanted to know.

"Keep your child quiet, Edith."

"Yes, dear."

"I'm going on a picnic, a wanderjahr. Anyone who wants to come along is invited. But I refuse to deviate by as much as a million miles from whatever trajectory suits me. I bought this ship from money earned in spite of the combined opposition of my whole family; I did not touch one thin credit of the money I hold in trust for our two young robber barons - and I don't propose to let them run the show."

Dr. Stone said quietly, "They merely asked where we were going. I would like to know, too."

"So they did. But why? Castor, you want to know so that you can figure a cargo, don't you?"

"Well - yes. Anything wrong with that? Unless we know what market we're taking it to, we won't know what to stock."

"True enough. But I don't recall authorising any such com­mercial ventures. The Rolling Stone is a family yacht."

Pollux cut in with, "For the love of Pete, Dad! With all that cargo space just going to waste, you'd think that -"

"An empty hold gives us more cruising range."

"But -"

"Take it easy. This subject is tabled for the moment. What do you two propose to do about your education?"

Castor said, "I thought that was settled. You said we could go along."

"That part is settled. But we'll be coming back this way in a year or two. Are you prepared to go down to Earth to school then - and stay there - until you get your degrees?"

The twins looked at each other; neither one of them said anything. Hazel butted in: "Quit being so offensively orthodox, Roger. I'll take over their education. I'll give them the straight data. What they taught me in school darn near ruined me, before I got wise and started teaching myself."

Roger Stone looked bleakly at his mother. "You would teach them, all right. No, thanks, I prefer a somewhat more normal approach."

""Normal!" Roger, that's a word with no meaning."

"Perhaps not, around here. But I'd like the twins to grow up as near normal as possible."

"Roger, have you ever met any normal people? I never have. The so-called normal man is a figment of the imagination; every member of the human race, from Jojo the cave man right down to that final culmination of civilisation, namely me, has been as eccentric as a pet coon - once you caught him with his mask off."

"I won't dispute the part about yourself."

"It's true for everybody. You try to make the twins "normal" and you'll simply stunt their growth."

Roger Stone stood up. "That's enough. Castor, Pollux - come with me. Excuse us, everybody."

"Yes, dear."

"Sissy," said Hazel. "I was just warming up to my rebuttal."

He led them into his study, closed the door. "Sit down."

The twins did so. "Now we can settle this quietly. Boys, I'm quite serious about your education. You can do what you like with your lives - turn pirate or get elected to the Grand Council. But I won't let you grow up ignorant."

Castor answered, "Sure, Dad, but we do study. We study all the time. You've said yourself that we are better engineers than half the young snots that come up from Earth."

"Granted. But it's not enough. Oh, you can learn most things on your own but I want you to have a formal, disciplined, really sound grounding in mathematics."

"Huh? Why, we cut our teeth on differential equations!"

Pollux added, "We know Hudson's Manual by heart We can do a triple integration in our heads faster than Hazel can. If there's one thing we do know, it's mathematics."

Roger Stone shook his head sadly. "You can count on your fingers but you can't reason. You probably think that the interval from zero to one is the same as the interval from ninety-nine to one hundred."

"Isn't it?"

"Is it? If so, can you prove it?" Their father reached up to the spindles on the wall, took down a book spool, and inserted it in the to his study projector. He spun the selector, stopped with a page displayed on the wall screen. It was a condensed chart of fields of mathematics invented, thus far by the human mind. "Let's see you find your way around that page."

The twins blinked at it. In the upper left-hand corner of the chart they spotted the names of subjects they had studied; the rest of the array was unknown territory; in most cases they did not even recognise the names of the subjects. In the ordinary engineering forms of the calculus they actually were adept; they had not been boasting. They knew enough of vector analysis to find their way around unassisted in electrical engineering and electronics; they knew classical geometry and trigonometry well enough for the astrogating of a space ship, and they had had enough of non-Euclidean geometry, tensor calculus, statistical mechanics, and quantum theory to get along with an atomic power plant

But it had never occurred to them that they had not yet really penetrated the enormous and magnificent field of mathematics.

"Dad," asked Pollux in a small voice, "what's a "hyperideal"?"

"Time you found out."

Castor looked quickly at his father. "How many of these things have you studied, Dad?"

"Not enough. Not nearly enough. But my sons should know more than I do."

It was agreed that the twins would study mathematics inten­sively the entire time the family was in space, and not simply under the casual supervision of their father and grandmother but formally and systematically through I.C.S. correspondence courses ordered up from Earth. They would take with them spools enough to keep them busy for at least a year and mail their completed lessons from any port they might touch. Mr. Stone was satisfied, being sure in his heart that any person skilled with mathematical tools could learn anything else he needed to know, with or without a master.

"Now, boys, about this matter of cargo-"

The twins waited; he went on: "I'll lift the stuff for you -"

"Gee, Dad, that's swell!"

"- at cost."

"You figure it and I'll check your figures. Don't try to flum­mox me or I'll stick on a penalty. If you're going to be businessmen, don't confuse the vocation with larceny."

"Right, sir. Uh... we still can't order until we know where we are going."

"True. Well, how would Mars suit you, as the first stop?"

"Mars?" Both boys got far-away looks in their eyes; their lips moved soundlessly.

"Well? Quit figuring your profits; you aren't there yet"

"Mars? Mars is fine, Dad!"

"Very well. One more thing: fail to keep up your studies and I won't let you sell a tin whistle."

"Oh, we'll study!" The twins 'got out while they were ahead. Roger Stone looked at the closed door with a fond smile on his face, an expression he rarely let them see, Good boys! Thank heaven he hadn't been saddled with a couple of obedient, well-behaved little nincompoops!