All 6 Uses of

hypothesis
in
Atlas Shrugged

"There's a market for Rearden Metal and I intend to take full advantage of it."
"Isn't the market somewhat hypothetical? The public response to your metal has not been encouraging."
Chpt 1.7 *

hypothetical = based on assumptions rather than facts

I have a hypothesis about it-I'll explain it to you afterwards, when I've put it to the test.
Chpt 2.4

hypothesis = a seemingly reasonable, but unproven, idea or explanation

"Miss Taggart," he asked sadly and cautiously, "would you say that if--this is just a hypothetical question--if the equipment now in use on the Rio Norte Line were made available, it would fill the needs of our transcontinental main-line traffic?"
Chpt 2.5 *

hypothetical = based on something temporarily treated as true to advance a discussion or to further investigation

Miss Taggart, I had been working on it for months, on that one particular hypothesis, and the more I worked, the more hopeless it seemed to become.†
Chpt 3.1

And all men use them, because they are true of being qua being......For a principle which every one must have who understands anything that is, is not a hypothesis......Evidently then such a principle is the most certain of all; which principle this is, let us proceed to say.†
Chpt 3.10

Definitions:

(1) (hypothesis as in: a study to test her hypothesis)
a seemingly reasonable, but unproven idea or explanation based upon known facts

In casual conversation, theory is a synonym for hypothesis, but a scientist would say that a hypothesis needs to pass rigorous tests before it could be accepted as a theory.
(2) (hypothesis as in: assume as a working hypothesis)
something that may or may not be true, but is temporarily treated as true to advance a discussion or to further investigation

This sense of hypothesis is typically seen in the form, hypothetical, or hypothetically.