Not a whit, Touchstone; those that are good manners at the court are as ridiculous in the country as the behaviour of the country is most mockable at the court. (III, ii)

The natural world of Arden is used in the play as a contrast to the civilized courtly life. Shakespeare initially presents an idealized version of "country" life, but later also includes negative aspects. Here Corin highlights the vast difference between the two ways of life in a conversation with Touchstone. The gist of the conversation seems to be that wherever you choose to live, it is what you make of it that is important.

All the world's a stage,
And all the men and women merely players;
They have their exits and their entrances;
And one man in his time plays many parts,
His acts being seven ages...
(II, vii)

The beginning of the play's most famous quote, the pessimistic Jaques meditates on the seeming predictabilty and futility of life. In each of man's "acts" he is worthy of ridicule and powerless.

Well, I will forget the condition of my estate, to rejoice in yours.
(I, ii)

Rosalind can be juxtaposed with Jaques, in that she sees the good things in life, and is not overwhelmed with the kind of negative observations made by Jaques. Confronted with the banishment of her father and the treachery of her uncle, she nonetheless speaks these words to Celia, demonstrating her ability to find something good amidst other hardships.

Twice did he turn his back, and purpos'd so;
But kindness, nobler ever than revenge,
And nature, stronger than his just occasion,
Made him give battle to the lioness,
Who quickly fell before him; in which hurtling
From miserable slumber I awak'd.
(IV, iii)

Spoken by Oliver, this quote is a good example of the theme of Christian virtue found in the play. He is referring to Orlando, who, despite his mistreatment by Oliver, saves him from the sleeping beast. This in turn, results in a reformed and "Christianized" Oliver.

...but it is a melancholy of mine own, compounded of many simples, extracted from many objects: and, indeed, the sundry contemplation of my travels; in which my often rumination wraps me in a most humorous sadness
(IV, i)

Jaques explains to Rosalind that his melancholy is all his own, arrived at from his experience and self-absorbtion. He is melancholic because he is Jaques, juxtaposed with Rosalind's goodness.

full of ambition, an envious emulator of every man's good parts, a secret and villainous contriver against me his natural brother:
(I, i)

Oliver's unfounded description of his brother Orlando at the beginning of the play, it is in fact a more fitting description of Oliver himself. At the end of the play, of course, Oliver is reformed through the good deeds of the very brother he vilifies here.

Virtue is no horn-maker; and my Rosalind is virtuous.
(IV, i)

Spoken by Orlando to "Ganymed" -- who is actually Rosalind in disguise. The quote is simply one example of many ironically comic exchanges that take place in the play.