Kramer leaned back. "You can see the situation. How can we deal with a factor like this? The perfect variable."  "Perfect? Prediction should still be possible. A living thing still acts from necessity, the same as inanimate material. But the cause-effect chain is more subtle; there are more factors to be considered. The difference is quantitative, I think. The reaction of the living organism parallels natural causation, but with greater complexity."  Gross and Kramer looked up at the board plates, suspended on the wall, still dripping, the images hardening into place. Kramer traced a line with his pencil.  "See that? It's a pseudopodium. They're alive, and so far, a weapon we can't beat. No mechanical system can compete with that, simple or intricate. We'll have to scrap the Johnson Control and find something else."  "Meanwhile the war continues as it is. Stalemate. Checkmate. They can't get to us, and we can't get through their living minefield."  Kramer nodded. "It's a perfect defense, for them. But there still might be one answer."  "What's that?"  "Wait a minute." Kramer turned to his rocket expert, sitting with the charts and files. "The heavy cruiser that returned this week. It didn't actually touch, did it? It came close but there was no contact."  "Correct." The expert nodded. "The mine was twenty miles off. The cruiser was in space-drive, moving directly toward Proxima, line-straight, using the Johnson Control, of course. It had deflected a quarter of an hour earlier for reasons unknown. Later it resumed its course. That was when they got it."  "It shifted," Kramer said. "But not enough. The mine was coming along after it, trailing it. It's the same old story, but I wonder about the contact."