Compare David's Uncle Axel to his Uncle Angus Mortan in The Chrysalids.

Throughout the story, Uncle Axel is a comfort to David. He
provides security for David (both physically and emotionally); he is able to confide in
Uncle Axel his ability to communicate telepathically, and Uncle Axel ensures David's
secret remains safe. David refers to him as his "best friend" when he is introduced in
chapter two.

Because of his experience as a sailor, Uncle
Axel's views are progressive comparatively to everyone else is
Waknuk:

They
all have pretty much the same legends of the Old People as we have -- how they could
fly, how they used to build cities that floated on the sea, how any one of them could
speak to any other, even hundreds of miles away, and so on. But what's more worrying is
that most of them -- whether they have seven fingers, or four arms, or hair all over, or
six breasts, or whatever it is that's wrong with them -- think that their type is the
true pattern of the Old People, and anything different is a
Deviation.

That seems silly at first, but when you find
more and more kinds just as convinced of it as we are ourselves -- well, you begin to
wonder a bit. You start asking yourself: well, what real evidence have
we got about the true image? You find that the Bible doesn't say anything to
contradict the people of that time being like us, but on the other hand it doesn't give
any definition of Man, either. No, the definition comes from Nicholson's
Repentances -- and he admits that he was writing some generations after
Tribulation came, so you find yourself wondering whether he knew he
was in the true image, or whether he only thought he was. [...] Uncle Axel went on
talking about the doubts of the true image that his voyage had given him (Chap
6).

While Uncle Axel has
doubts about the image of man and the beliefs of Waknuk, he generally keeps these
concepts to himself. While he discusses it with David, this discourse is held privately.
Uncle Axel keeps his progressive views to
himself.

Comparatively, Uncle Angus Morton also has a
progressive view about the image of man and the beliefs of Waknuk, but he frequently
takes actions that draws attention to his differences in
belief.

My
father had been heard to sum up his opinion by declaring that if Angus had any
principles they were of such infinite width as to be a menace to the rectitude of the
neighbourhood; to which Angus was reputed to have replied that Joseph Strorm was a
flinty-souled pedant, and bigoted well beyond reason. It was not, therefore, difficult
for a row to blow up, and the latest one occurred over Angus' acquisition of a pair of
great-horses.

Rumours of great-horses had reached our
district though none had been seen there. My father was already uneasy in his mind at
what he had heard of them, nor was the fact that Angus was the importer of them a
commendation; consequently, it may have been with some prejudice that he went to inspect
them.

His doubts were confirmed at once. The moment he set
eyes on the huge creatures standing twenty-six hands at the shoulder, he knew they
were wrong. He turned his back on them with disgust, and went
straight to the inspector's house with a demand that they should be destroyed as
Offences.(Chap 4)

While both
Uncle Axel and Uncle Angus Morton challenge the beliefs of Waknuk, only Uncle Angus
Morton does so publicly.