"You've asked a very delicate question," Dr. O'Connor said. "Actually, we can't be quite positive." His expression showed just how little he wanted to make this admission. "However," he went on, brightening, "there is some evidence which seems to show that it is basically the same process as psychokinesis. And we do have quite a bit of empirical data on psychokinesis." He scribbled something on a sheet of paper and said: "For instance, there's this." He held the paper up to the screen so that Malone could read it. It said: md ----- = K ft2 Malone looked at it for some seconds. At last he said: "It's very pretty. What is it?" "This," Dr. O'Connor said, in the tone of voice that meant You Should Have Known All Along, But You're Just Hopeless, "is the basic formula for the phenomenon, where _m_ is the mass in grams, _d_ is the distance in centimeters, _f_ is the force in dynes and _t_ is the time in seconds. _K_ is a constant whose value is not yet known." Malone said: "Hm-m-m," and stared at the equation again. Somehow, the explanation was not very helpful. The value of _K_ was unknown. He understood that much, all right but it didn't seem to do him any good. "As you can see," Dr. O'Connor went on, "the greater the force, and the longer time it is applied, the greater distance any mass can be moved. Or, contrariwise, the more mass, the greater mass, that is, the easier it is to move it any given distance. This is, as you undoubtedly understand, not at all in contradistinction to physical phenomena." "Ah," Malone said, feeling that something was expected of him, but not being quite sure what. Dr. O'Connor frowned. "I must admit," he said, "that the uncertainty as to the constant _k_, and the lack of any real knowledge as to just what kind of force is being applied, have held up our work so far." Then his face smoothed out. "Of course, when we have the teleports to work with, we may derive a full set of laws which--" "Never mind that now," Malone said. "But our work is most important, Mr. Malone," Dr. O'Connor said with a motion of his eyebrows. "As I'm sure you must understand." "Oh," Malone said, feeling as if he'd been caught without his homework, "of course. But if you don't mind--" "Yes, Mr. Malone?" Dr. O'Connor said smoothly. "What I want to know," Malone said, "is this: what are the limitations of this ... uh ... phenomenon?" Dr. O'Connor brightened visibly. "The limitations are several," he said. "In the first place, there is the force represented by _f_ in the equation. This seems to be entirely dependent on the ... ah ... strength of the subject's personality. That is if we assume that the process is at all parallel with the phenomena of psychokinesis and levitation. And there are excellent theoretical reasons for so believing." "In other words," Malone said, "a man with a strong will would be able to exert more force than a weaker-willed man?"