Daneel said, "I do not understand you, friend Giskard."
"I am not surprised. I am not certain I understand myself. But consider - when we think of the humanity we must save, we think of Earthpeople and the Settlers. They are more numerous than the Spacers, more vigorous, more expansive. They show more initiative because they are less dependent on robots. They have a greater potential for biological and social evolution because they are shorter-lived, though long-lived enough to contribute great things individually."
"Yes," said Daneel, "you put it succinctly."
"And yet the Earthpeople and the Settlers seem to possess a mystical and even irrational confidence in the sanctity and inviolability of Earth. Might not this mystique be as fatal to their development as the mystiques, of robots and long life that hobble the Spacers?"
"I had not thought of this," said Daneel. "I do not know."
Giskard said, "If you were as aware of minds as I am, you would have been unable to avoid thinking of this. How does one choose?" he went on with sudden intensity. "Think of humanity as divided into two species: the Spacers, with one apparently fatal mystique, and the Earthpeople plus the Settlers, with another possibly fatal mystique. It may be that there will be other species, in the future, with even less attractive properties.
"It is not sufficient to choose, then, friend Daneel. We must be able to shape. We must shape a desirable species and then protect it, rather than finding ourselves forced to select among two or more undesirabilities. But how can we achieve the desirable unless we have psychohistory, the science I dream of and cannot attain?"
Daneel said, "I have not appreciated the difficulty, friend Giskard, of possessing the ability to sense and influence minds. Is it possible that you learn too much to allow the Three Laws of Robotics to work smoothly within you?"
"That has always been possible, friend Daneel, but not until these recent events has the possibility become actual. I know the pathway pattern that produces this mind-sensing and mind-influencing effect within me. I have studied myself carefully for decades in order that I might know it and I can pass it on to you so that you might program yourself to be like me - but I have resisted the urge to do so. It would be unkind to you. It is enough that I bear the burden."
Daneel said, "Nevertheless, friend Giskard, if ever, in your judgment, the good of humanity would require it, I would accept the burden. Indeed, by the Zeroth Law, I would be obliged to."
Giskard said, "But this discussion is useless. It seems apparent that the crisis is nearly upon us - and since we have not even managed to work out the nature of the crisis - "
Daneel interrupted. "You are wrong, there at least, friend Giskard. I now know the nature of the crisis."
91
One would not expect Giskard to show surprise. His face was, of course, incapable of expression. His voice possessed modulation, so that his speech sounded human and was neither monotonous nor unpleasant. That modulation, however, was never altered by emotion in any recognizable way.
Therefore, when he said, "Are you serious?" it sounded as it would have had he expressed doubt over a remark Daneel had made concerning what the weather would be like the next day. Yet, from the manner in which his head turned toward Daneel, the way in which one hand lifted, there was no doubt that he was surprised.
Daneel said, "I am, friend Giskard."
"How did the information come to you?"
"In part, from what I was told by Madam Undersecretary Quintana at the dinner table."
"But did you not say that you had obtained nothing helpful from her, that you supposed you had asked the wrong questions?"
"So it seemed in the immediate aftermath. On further reflection, however, I found myself able to make helpful deductions from what she had said. I have been searching Earth's central encyclopedia through the computer outlet these past few hours - "
"And found your deductions confirmed?"
"Not exactly, but I found nothing that would refute them, which is perhaps the next best thing."
"But is negative evidence sufficient for certainty?"
"It is not. And therefore I am not certain. Let me tell you, however, my reasoning and if you find it faulty, say so."
"Please proceed, friend Daneel."
"Fusion power, friend Giskard, was developed on Earth before the days of hyperspatial travel and, therefore, while human beings were to be found, only on the one planet, Earth. This is well known. It took a long time to develop practical controlled fusion power after the possibility had first been conceived and put on a sound scientific footing. The chief difficulty in converting the concept into practice involved the necessity of achieving a sufficiently high temperature in a sufficiently dense gas for a long enough time to bring about fusion ignition.
"And yet several decades before controlled fusion power had been established, fusion bombs had existed - these bombs representing an uncontrolled fusion reaction. But controlled or uncontrolled, fusion could not take place without an extremely high temperature in the millions of degrees. If human beings could not produce the necessary temperature for controlled fusion power, how could they do so for an uncontrolled fusion explosion?
"Madam Quintana told me that before fusion existed on Earth, there was another variety of nuclear reaction in existence - nuclear fission. Energy was derived from the splitting - or fission - of large nuclei, such as those of uranium and thorium. That, I thought, might be one way of achieving a high temperature.
"The encyclopedia I have this night been consulting gives very little information about nuclear bombs of any sort and, certainly, no real details. It is a taboo subject, I gather, and it must be so on all worlds, - for I have never read of such details on Aurora either, even though such bombs still exist. It is a part of history that human beings are ashamed of, or afraid of, or both, and I think this is rational. In what I did read of fusion bombs, however, I read nothing about their ignition that would have eliminated the fission bomb as the igniting mechanism. I suspect, then, that based, in part, on this negative evidence, the fission bomb was the igniting mechanism.