From "Manual of Muad'Dib" by the Princess Irulan

So that's the dream of this Liet-Kynes , she thought. And she said: "Bribes are dangerous; they have a way of growing larger and larger."
"They grow," he said, "but the slow way is the safe way."
Jessica turned, looked out over the basin, trying to see it the way Stilgar was seeing it in his imagination. She saw only the grayed mustard stain of distant rocks and a sudden hazy motion in the sky above the cliffs.
"Ah-h-h-h," Stilgar said.
She thought at first it must be a patrol vehicle, then realized it was a mirage—another landscape hovering over the desert-sand and a distant wavering of greenery and in the middle distance a long worm traveling the surface with what looked like Fremen robes fluttering on its back.
The mirage faded.
"It would be better to ride," Stilgar said, "but we cannot permit a maker into this basin. Thus, we must walk again tonight."
Maker—their word for worm , she thought.
She measured the import of his words, the statement that they could not permit a worm into this basin. She knew what she had seen in the mirage—Fremen riding on the back of a giant worm. It took heavy control not to betray her shock at the implications.
"We must be getting back to the others," Stilgar said. "Else my people may suspect I dally with you. Some already are jealous that my hands tasted your loveliness when we struggled last night in Tuono Basin ."
"That will be enough of that!" Jessica snapped.
"No offense," Stilgar said, and his voice was mild. "Women among us are not taken against their will . . . and with you . . . " He shrugged. ". . . even that convention isn't required."
"You will keep in mind that I was a duke's lady," she said, but her voice was calmer.
"As you wish," he said. "It's time to seal off this opening, to permit relaxation of stillsuit discipline. My people need to rest in comfort this day. Their families will give them little rest on the morrow."
Silence fell between them.
Jessica stared out into the sunlight. She had heard what she had heard in Stilgar's voice—the unspoken offer of more than his countenance . Did he need a wife? She realized she could step into that place with him. It would be one way to end conflict over tribal leadership—female properly aligned with male.
But what of Paul then? Who could tell yet what rules of parenthood prevailed here? And what of the unborn daughter she had carried these few weeks? What of a dead Duke's daughter? And she permitted herself to face fully the significance of this other child growing within her, to see her own motives in permitting the conception. She knew what it was—she had succumbed to that profound drive shared by all creatures who are faced with death—the drive to seek immortality through progeny. The fertility drive of the species had overpowered them.
Jessica glanced at Stilgar, saw that he was studying her, waiting. A daughter born here to a woman wed to such a one as this man—what would be the fate of such a daughter? she asked herself. Would he try to limit the necessities that a Bene Gesserit must follow?
Stilgar cleared his throat and revealed then that he understood some of the questions in her mind. "What is important for a leader is that which makes him a leader. It is the needs of his people. If you teach me your powers, there may come a day when one of us must challenge the other. I would prefer some alternative."
"There are several alternatives?" she asked.
"The Sayyadina," he said. "Our Reverend Mother is old."
Their Reverend Mother!
Before she could probe this, he said: "I do not necessarily offer myself as mate. This is nothing personal, for you are beautiful and desirable. But should you become one of my women, that might lead some of my young men to believe that I'm too much concerned with pleasures of the flesh and not enough concerned with the tribe's needs. Even now they listen to us and watch us."
A man who weighs his decisions, who thinks of consequences , she thought.
"There are those among my young men who have reached the age of wild spirits," he said. "They must be eased through this period. I must leave no great reasons around for them to challenge me. Because I would have to maim and kill among them. This is not the proper course for a leader if it can be avoided with honor. A leader, you see, is one of the things that distinguishes a mob from a people. He maintains the level of individuals. Too few individuals, and a people reverts to a mob."
His words, the depth of their awareness, the fact that he spoke as much to her as to those who secretly listened, forced her to reevaluate him.