Discuss the Pip-Estella relationship in Great Expectations. What bearing does it have on the theme of the novel?

In Great Expectations, Mr. Jaggers
advises Pip, "Take nothing on appearances."  Certainly, the Pip-Estella relationship is
an example of the Appearances vs. Reality  theme that prevails thoughout Charles
Dickens's classic novel.

From the first meeting of Pip with
Estella, Pip falls victim to believing in appearances.  The beautiful, haughty girl
whose name means "star" is elevated in Pip's esteem simply because she lives with the
rich Miss Havisham and is dressed in lovely clothes and speaks in a deprecating way to
him, calling him "common."  Immediately, because this vision of superior loveliness who
speaks properly has termed him "common," Pip experiences a humiliation.  But, despite
her cruel ways, Pip falls hopelessly in love with the beautiful Estella, perhaps even
because she is unattainable.  He perpetuates his delusions by hoping that if he becomes
a gentleman, Estella will accept him as an equal and requite his
love.

Of course, the truth is that from the beginning,
Pip's birth has more legitimacy than that of Estella's.  For, his parents were married
and, albeit poor, they were certainly not criminals as are the parents of Estella, whose
birth came out of the streets of London.

In addition to the
theme of Appearance vs. Reality, the relationship of Pip and Estella also points
to a salient theme in the works of Dickens:  Class Stratification.  The theme of social
class is central to Great Expectations as it acts as extends into the other themes such
as the Appearance theme.  Pip's angst over being "common," as Estella has labeled him,
is his driving force to become a gentleman and entertain the "great expectations" of
having bettered himself sufficiently so that he will become worthy of Estella.  But, of
course the class structure is a false one in Great
Expectations, thus paralleling the Appearance vs. Reality theme, as
Pip later learns; rather, it is what one is as a person that is truly of value. 
Estella, for all her beauty and daintiness is but common in her heart; she is incapable
of noble thoughts and acts while Joe, the humble blacksmith is truly a good and noble
man.