"That's right, but it's not a mathematical proposition. It's a sociological observation and there is always the possibility of exceptions to such observations."
Amadiro scowled. "The best road to safety lies with being done with this project. You said you'd be ready today."
"That, too, is a sociological observation, Dr. Amadiro. I should be ready today. I would like to be. I cannot guarantee it mathematically."
"How long before you can guarantee it?"
Mandamus spread his hands in a "Who knows?" gesture. "Dr. Amadiro, I am under the impression I have already explained this, but I'm willing to go through it again. It took me seven years to get this far. I have been counting on some months yet of personal observations at the fourteen different relay stations on Earth's surface. I can't do that now because we must finish before we are located and, possibly, stopped by the robot Giskard. That means I have to do my checking by communicating with our own humanoid robots at the relays. I can't trust them as I would myself. I must check and recheck their reports and it is possible that I may have to go to one or two places before I am satisfied. That would take days - perhaps a week or two."
"A week or two. Impossible! How long do you think I can endure this planet, Mandamus?"
"Sir, on one of my previous visits I stayed on this planet for nearly a year - on another, for over four months."
"And you liked it?"
"No, sir, but I had a job to do and I did it - without sparing myself." Mandamus stared coldly at Amadiro.
Amadiro flushed and said in a somewhat chastened tone, "Well, then, where do we stand?"
"I'm still weighing the reports that are coming in. We are not working with a smoothly designed laboratory-made system, you know. We have an extraordinary heterogeneous planetary crust to deal with. Fortunately, the radioactive materials are widely spread, but in places they run perilously thin, and we must place a relay in such places and leave robots in charge. If those relays are not, in every case, properly positioned and in proper order, the nuclear intensification will die out and we will have wasted all these painful years of effort on nothing. Or else, there may be a surge of localized intensification that will have the force of an explosion that will blow itself out and leave the rest of the crust unaffected. In either case, total damage would be insignificant.
"What we want, Dr. Amadiro, is to have the radioactive materials and, therefore, significantly large sections of earth's crust grow - slowly - steadily - irreversibly - he bit the words off as he pronounced them in spaced intervals - more and more intensely radioactive, so that Earth becomes progressively, more unlivable. The social structure of the planet will break down and the Earth, as an effective abode of humanity, will be over and done with. I take it, Dr. Amadiro, that this is what you want. - It is, what I described to you years ago and what you said, at that time, you wanted."
"I still do, Mandamus. Don't be a fool."
"Then bear with the discomfort, sir - or else, leave and I will carry on for whatever additional time it takes."
"No, no," muttered Amadiro. "I must be here when it's done - but it can't help being impatient. How long have you decided to allow the process to build? - I mean, once you initiate the original wave of intensification, how long before Earth becomes uninhabitable?"
"That depends on the degree of intensification I apply initially. I don't know, just yet, what degree will be required, for that depends on the overall efficiency of the relays, so I have prepared a variable control. What I want to arrange is a lapse period of ten to twenty decades."
"And, if you allow a smaller lapse period?"
"The less the lapse period we allow, the more rapidly portions of the crust will grow radioactive and the more rapidly the planet will warm up and grow dangerous. And that means the less likely it will be that any significant number of its population can be removed in time."
"Does that matter?" murmured Amadiro.
Mandamus frowned. "The more rapidly the Earth deteriorates, the more likely it is that Earthpeople and Settlers will suspect a technological cause - and that we are the likely ones to receive the blame. The Settlers will then attack us with fury and, in the cause of their holy world, they will fight to extinction, provided only that they can inflict substantial harm on us. This is something we have discussed before and it seems we agreed on the matter. It would be far better to allow ample time, during which we can prepare for the worst and during which a confused Earth may assume that the slowly increasing radioactivity is some natural phenomenon they don't understand. That is something that has become more urgent today than yesterday, in my judgment.
"Is that so?" Amadiro was frowning also. "You have that sour, puritanical look that makes me sure you have found a way to place the responsibility for that on my shoulders."
"With respect, sir, that is not difficult in this case. It was unwise to send out one of our robots to destroy Giskard."
"On the contrary, it had to be done. Giskard is the only one who might destroy us."
"He must find us first - and he won't. And even if he does, we are knowledgeable roboticists. Don't you think we could handle him?"
"Indeed?" said Amadiro. "So Vasilia thought and she knew Giskard better than we - and yet she couldn't handle him. And somehow the warship that was to take him into charge and destroy him at a distance could not handle him."
"So he has now landed on Earth. One way or another, he must be destroyed."
"He has not been. There has been no report of it."