The main idea of "The Selfish Giant" by Oscar Wilde is encompassed by the phrase spoken by the Giant in the story
'I have many beautiful flowers,' he said; 'but the children are the most beautiful flowers of all.'
This story is one of the many allegorical tales in which Wilde infuses parables in order to imitate the way that Jesus would have combined a message with a story.
Although Wilde was not conventionally a religious man, the elements of rite and sermons were some of the concepts about the Catholic faith that would fascinate Wilde the most.
However, Wilde was particularly interested in the thought of Jesus speaking in parables. Hence, Wilde also uses epigrams and paradoxes in a similar way to cause the same effect of awe and surprise that the Bible would say Jesus used to cause.
"The Selfish Giant" is written following the parable of Jesus and the children, where Jesus tells to allow the children to go to him, for theirs is the kingdom of God.
In the story, a cold and angry Giant lives alone in a castle where a beautiful garden continues to tempt the children to go in and play. After being told off by the giant, the children cease going and the garden quits blooming, turning into an eternal winter.
The Giant is not at all moved by this until the day when he sees the children entering the garden again, cheering it up. However, it is when a very feeble kid tries to climb the tree that the Giant's heart melts, and he lends the small child a hand to climb the tree. Spring blooms again in his garden, but never sees the child again.
We find out later that the child was Jesus, himself, and that the Giant meets him again when he is about to enter paradise. It is then when he sees that the child has wounds in his hands and feet. The child represents the purity, innocence, and love that Jesus instills in our hearts. That is the thematic connection between children, love and innocence as the saviors of one's heart.
The thematic points are clear; the only way to allow love into your heart is by opening up to it. Another important point is that, although the Giant was unable to love, a miracle occurs in the form of a child (Jesus) showing him the way to find that love. Most importantly, the fact that the Giant allows the love of God into his heart is what, ultimately, leads him to paradise-regardless what his life had been like before.
Hence, "The Selfish Giant" certainly represents an early time in Wilde's literary career, when he was still trying to find himself, and his role, in the literary world. "Selfish Giant" uses religious undertones to convey the message of allowing love to flow into your heart, so that you can learn to love all that is around you.