The Galactic Empire Was Falling.
It was collssal Empire, stretching across millions of worlds from arm-end to arm-end of the mighty spiral that was the Milky Way.

Foundation and Empire

The First Galactic Empire had endured for tens of thousands of years.

"Prologue", Second Foundation

"Why did I do it?" asked Golan Trevize.
It wasn't a new question. Since he had arrived at Gaia, he had asked it of himself frequently.

Foundation and Earth

Passages

Q. You do not consider your statement a disloyal one?
A. No, sir. Scientific truth is beyond loyalty and disloyalty.

"Violence," came the retort, "is the last refuge of the incompetent."

Never let your sense of morals prevent you from doing what is right!

Foundation

It is the invariable lesson to humanity that distance in time, and in space as well, lends focus. It is not recorded, incidentally, that the lesson has ever been permanently learned.

And there she was, age fourteen plus, weary enough for eighty plus, frightened enough for five minus.

The most hopelessly stupid man is he who is not aware that he is wise.

Second Foundation

My crime is that I have never labored to make myself popular — I admit that much — and I have paid too little attention to fools who are old enough to be senile but young enough to have power.

Foundation's Edge