Unlike what I thought, writing about Caddy is difficult. Because I have very strong feelings about her. But I'm going to try anyway.
William Faulker has a rather unusual way of characterising Caddy- she's the central character of "The sound and the fury", in which each of the 1st 3 parts is a response to her, but she's entirely absent throughout the narrations and we never get to know her side of the story. So, as we can't enter her mind and don't know what she thinks and how she feels and why she does what she does, as we're unable to see things from her point of view, our understanding of her personality and perception of her character is shaped by her brothers' feelings. On the 1 hand it's fascinating, we can see her from different angles. To Jason she's a shame of the family, sexually promiscuous, wild and careless, who ruins his future and who must take all the blame for his present situation. To Benjy she's a gentle, loving, considerate sister, not just the only person who loves him genuinely but also the only person who always understands him and takes the job of voicing his needs and wishes. She cares about him and loves him unconditionally, giving him the love and understanding he can't get from anyone else (Dilsey does care about him but doesn't have that understanding), she also takes the place of a mother (because their mother's immersed in her own world, in her hypochondria, illusion and self-pity). To Quentin, well, she's everything*: sister, close friend, mother, Madonna, whore, perhaps even lover, but most certainty the centre of his world, and he projects into her all of his ideals and expectations, his Southern code of honour, his ideas about purity and innocence. He has conflicted feelings about her, which cause his depression and which finally lead to his self-destruction.
Thus, even though one may think the characterisation of Caddy is somehow incomplete, these 3 perspectives present her to us real and deeply heartbreaking just the same, showing us various aspects of Caddy- her love, tenderness, passion, free spirit, her complexity.
On the other hand, by placing Caddy elsewhere and letting her brothers talk about her, the book creates a certain distance between her and the readers and makes us share the same longing for her as her brothers. In the end, when Caddy has gone for good, leaving no trace and the last section has merely void and decay without any love or warmth or hope, we realise how bad things are without her.
And how little we know about her, it makes us miss her.
*: This reminds me of a passage Buddy writes about his brother Zooey Glass "... He was a great many things to a great many people while he lived, and virtually all things to his brothers and sisters in our somewhat outsized family. Surely he was all real things to us: our blue-striped unicorn, our portable conscience, our supercargo, and our 1 full poet..."
I can't help noticing that, whether or not Salinger had read this novel before creating the Glass family saga, the characterisation of Zeymour Glass is strikingly similar to that of Caddy, i.e through his siblings' memories, thoughts and emotions.