Why haven't the clothes on the waxworks in the room where Jadis is sleeping rotted away? Because the Deplorable Word killed all the bacteria to do the rotting!
The entire series is a biblical metaphor for children. Why does Aslan name the Cabbie king? "Blessed are the meek, for they shall inherit the Earth."
The Bell in Charn doesn't need special magic to MAKE people ring it. Most people would be tempted by those words. What's important is that somebody who had the power to get there and yearned for knowledge and could be tempted despite warnings came along and rang that Bell.
Five-Second Foreshadowing: the three people who sing a hymn praising for letting crops grow while they are in a dark emptiness where nothing of the sort has ever happened (yet) are the same ones who enjoy the creation of a new world they witness just after they have finished "with open mouths and shining eyes". The other travelers (who are not the sort to have sentiments like these) don't, but instead are rather frightened.
This continues into what the travelers get from the trip. Of the three people who (pre-emptively) join in the creation song with praise for what is created, Frank (who has a hard life in the city) gets a new and better home, Polly (who comes across as rather lonely) gets a new best friend, and Digory (whose mother is deathly ill) is gifted a panacea. While Jadis gets cursed and Andrew just gets to make himself ridiculous.
What happens at the end of The Last Battle to those coming in at the stable door also happens to both Digory and Uncle Andrew in this book: they look at Aslan and basically judge themselves. The result in each case is diametrically opposite: while Andrew "has made himself unable to hear [Aslan's] voice", is overcome with terror, and Aslan can do nothing about him shutting himself up in his own misery; Digory owns up, reconciles, and gets the chance for a Redemption Quest — foreshadowing both the two things that happen in The Last Battle.
In-universe. Digory is about to run off exploring other worlds when Polly thinks to mark the pool they came from. The thought of what might have happened if she hadn't thought of it — trapped and unable to find their way home in an infinite wood full of infinite pools of water all of which look exactly alike — scares Digory so badly he can barely use his knife to make the mark.
Anger Born of Worry: Why are Polly's parents so disproportionately angry at the notion of her splashing through puddles in an unknown park that they leave all the nice parts out of her dinner, send her to bed early, and threaten to make her stop meeting Digory (who's implied to be her only friend, and only since quite recently at that)? Modern readers can't relate to this at all, because the disease is all but extinct (except in very few places very far from London); but in those times, contaminated water (like puddles) often carried polio — which killed a lot of children and crippled many others for life. It would still be some decades before you could even protect yourself against it. Simply put, they're overreacting because they fear for her life.
When Aslan explains how apples from his garden do indeed grant wishes, but how the wish becomes twisted and rotten if the apple is stolen; he explains that had Digory taken one home to his mother as Jadis suggested, she would indeed have recovered just as Jadis said, but the future days in their lives would grow sour and finally become so horrible that Digory and his mother would both ultimately look back on that day and wish she had died instead. He thoroughly averts this by giving one to Digory as a gift.
Anything concerning the Deplorable Word. Just the Deplorable Word, period: an incantation that causes a planetary level extinction event, perhaps even universe level.
It's said that if Digory had taken an apple to his mother directly from the garden, the effects on his mother would essentially constitute a Fate Worse than Death. But that doesn't really make sense; the only thing that the poem at the gate says is that the fruit must be taken "for others" — how does Digory taking one for his mother (in other words, a person other than himself) not constitute taking the fruit "for others"?
By prioritizing the life of one person who happens to be important to him over the lives of every living creature in Narnia, Digory's actions would be inherently selfish. The life of one woman—yes, even his mother—is not more important than the life of a world.
More to the point, the admonition to only take the fruit for the sake of others is not what would have cursed Digory's apple; the apple he's given freely bears no such curse just because he's using it to heal someone he personally loves. "Take of my fruit for others" is the line Jadis violates. More applicable to Digory is the line against stealing. Whether his action was selfish or selfless doesn't matter; as Aslan says, someone with good intentions planting an apple for the sake of protecting Narnia would still bring down a twisted version of protection if the apple were stolen on purpose. How you do things matters just as much as why.
It still seems like the line between "stealing" and "taking with cause" is...less than clear.
You steal an apple when you take it without the orchard owner's permission. Some things are that simple.
This might be the same hidden orchard with the Healing Spring that briefly features in The Voyage of the Dawn Treader, where Eustace is taken by Aslan to be un-dragoned; and then again in The Last Battle as a gateway to "further up and further in". All three appearances in combination heavily imply it's Aslan's place.
Genius Bonus makes those implications even heavier: "paradise" means "walled garden", while "Eden" means "well-watered" — so from the description of the place, it's pretty clear whose permission you need to go in and take some of the fruit.
When Diggory does ask for permission (even though he's too shy to ask upfront) when he tells Aslan of Jadis' suggestion to take an apple for his mother; that said permission, and blessing, is granted quite freely; and the apple of life works without any curse attached at all.
That is what would have happened with a stolen apple. It's not what will happen now. [...] Go, pluck her an apple from the tree.
