probability--and life is chemical. Two atoms must come into more or less
violent contact before a union takes place, and cannot if they have
neither momentum nor inertia.

"Anyway--why worry. I can't do it, because I can't control this thing.
And we have the extra-space drive."

"How does that darned thing work? Can't you drop the math and tell me
about it?"

Kendall smiled. "Not too readily. Remember first, as to the driving
system, that it works on the fabric of space. Space is, in the physical
sense, a fabric woven of the threads of lines of force from every body
in the universe, made up of fields and forces. It is elastic, and can
transmit strains. But anything that can transmit strains, can be
strained against. With the tremendous field intensities available by the
material engines, I can get such fields as will 'dig their toes' into
space and push.

"That's the drive itself. It is accelerationless, because it enfolds us,
and acts equally on every atom of us. By maintaining in addition a
slight artificial gravity--thanks also to the intensity of those
material engine fields--we can be comfortable, while we accelerate at
tremendous rates.

"That is, I think, at least allied to the Stranger's system. For the
high-speed drive, I do in fact use the Uncertainty. I can control it in
a certain sense by determining its powers, and the limits of
uncertainty, whether First, Second, Third or Fourth Degree. It advances
in jumps--but on a finer plotting of the curve, you can see that each
jump represents a vast series of smaller jumps. That is, there is Class
A, B, C, D, and so forth Uncertainty of the First Degree. Now Class A
First Degree Uncertainty involves only the deepest, broadest principles.
Only they break down. One of these is the law of the speed of light.

"I'm sure that isn't the system the Strangers use, but I'm also sure
there's no limit to the speed we can get."

"Doesn't that wreck your drive system?"

"No, because gravity and the fields I use in driving are First Degree
Uncertainties of the higher classes.

"But at any rate, it will work. And--I suspect you came to say you were
ready to go."

"I did." McLaurin nodded.

"Still stick to your original plan?"

McLaurin nodded. "I think it's best. You follow those fellows back to
their system in the 'S Doradus' and I'll stay here in the 'Cepheid' to
protect the system. They may need some time to get out of the place
here. And remember, we ought to