Henry James's The Turn of the Screw is a much-discussed work of literature. Many critics label it as a ghost story, while others believe that the governess's sightings of Quint and Miss Jessel are merely hallucinations.
Those who question the governess's credibility do so on the premise that her hallucinations are products of her infatuation with the (absent) employer who has left her in charge of his niece and nephew--and who has told her that she is not to trouble him with news regarding their behavior, academic progress, etc.
When the governess first meets her employer, she observes that he is
a gentleman, a bachelor in the prime of life, such a figure as had never risen, save in a dream or an old novel, before a fluttered, anxious girl out of a Hampshire vicarage.
This description suggests that the governess has some degree of physical attraction to the children's uncle. Further, the governess is often described as "young" and "nervous," both of which are characteristics that might make the theory that her visions of ghosts are hallucinations more believable.
Literary critic Ryan Poquette notes that the governess frequently daydreams about "meeting someone," and that the employer's absence--and further, his insistence that the governess never contact him--has a great impact on the governess's state of mind. In expecting to see her employer in front of her, as a product of her daydream, the governess is shocked to see the image of Quint on the tower:
Her conscious mind is asking for the appearance of the master so that she can show him how good she is being and perhaps be rewarded. But it is the deeper, subconscious mind, freshly affected from all of her thoughts about how she wants to prove herself to the master, that precipitates the "ghostly" vision. In her mind, the governess is creating a challenge for herself, something that is greater than merely following the master's orders and something that will perhaps yield a greater reward, once the master sees how she has been victorious.
Again, there is no clear interpretation of James's The Turn of the Screw. However, there is much textual evidence to support the theory that the governess's credibility should be questioned.