Symbolism, Imagery, Allegory
That's Deep, Man.
This book is obsessed with depth.
The Governess is always going on about how she has greater depths, or the children have depths, or how the situation as a whole has depths that are as yet unexplained. Mrs. Grose also uses the word to describe her fear of Quint – she's afraid of him, she says, because he "was so clever – he was so deep" (6.10).
There are a couple of ways of reading this (the symbol of depth has, yes, depths).
The first has to do with the unknown: the repetitions of "depths" and "deep" in this book tend to allude to the fact that things and people are unknowable and undiscoverable.
This is unsettling enough with regular old adults, but the idea of children containing more that meets the eye is downright terrifying. An adult's "hidden depths" can refer to experience or biography: we can't know everything that everyone has ever done, so those depths are understandable. When it comes to kids, however, those depths are innate—when kids are deep, it's because they were essentially born mysterious.
The second reading is saucier, and gets to our buddy Edmund Wilson's reading of the Governess as so sexually repressed she's gone insane. Check out this quote:
“No, no—there are depths, depths! The more I go over it, the more I see in it, and the more I see in it, the more I fear. I don’t know what I don’t see—what I don’t fear!” (6.23)
First of all: holy verbal diarrhea, Batman. The Governess really sounds unhinged in this quote.
But second of all, notice how the "depths" that the Governess is talking about has to do with her own personal knowledge. She's saying that she is afraid, not only of the things she knows about and sees, but also of the things she doesn't know about and doesn't see. (Or rather, she's not afraid of what she doesn't know about, but she knows she should be. It's a pretty nuts statement.)
This can easily be applied to the theory that the Governess is repressed to the point of madness. She's scared of her own lack of experience in all (wink wink) things. This is underlined by the use of the word "depth," which can be seen as alluding to an anxiety regarding penetration or an anxiety regarding her own vagina.
Our suggestion: go grab a highlighter and mark every time you find a reference to "depth," or "deep" inyour copy of The Turn of the Screw. We're pretty sure you can find a deep—yep, we know that's low-hanging fruit—meaning of your own.