The titular bell jar In Sylvia Plath’s eponymous novel is symbolic of Esther’s condition because it serves as a metaphor for her depression. This symbolism is especially evident when the heroine reminiscences on her past experiences and reflects whether a “bell jar” would not descend upon her and distort her perception once again. The bell jar becomes a fitting symbol for depression because it is a barrier that, despite being fully transparent, is always there. Depression itself is a medical condition that does not manifest in evident physical symptoms, such as a rash or cough but is, nevertheless, completely real. Thus, the bell jar becomes a metaphor for a grave state of mind that oppresses and isolates Esther while staying mostly unnoticeable for those around her.
Another reason why the belle jar is symbolic of the heroine’s condition is also related to its transparency. One of the functions of the bell jar is decorative: it is meant to shield the objects from dust and other external impacts while also preserving their visibility – in other words, to display things safely. Esther, just as if she were under a bell jar, lives through her depressive experiences while being on display. For instance, one of the earliest manifestations of her depression comes during a photo-shoot, when she proves unable to hold a smile and bursts into tears instead. Thus, Esther’s depression begins when the heroine is on display, and anyone can see her. The heroine remains visible for everyone but grows increasingly lonely and depressed as she cannot make a human connection – just as an object under a bell jar, which one can look upon, but not touch.