As much as child e’er loved, or father found,
A love that makes breath poor and speech unable,
Beyond all manner of so much I love you. (I.i.)

When Lear asks his daughters to declare their love for him, this line is Goneril’s response. She says her love makes “speech unable,” even though she is in the middle of a speech about love. This contrast indicates that Goneril speaks insincerely. Lear’s inability to distinguish between empty flattery and truth introduces an important theme of the play: the unreliable nature of words.

You see how full of changes his age is. The observation we
have made of it hath not been little. He always loved our
sister most, and with what poor judgment he hath now cast her
off appears too grossly. (I.i.)

Goneril and Regan see their father Lear more clearly than he sees himself. Here Goneril explains Lear’s situation: as he ages, he is losing his ability to make good decisions. Goneril also sees that Cordelia is Lear’s favorite daughter.

He hath ever but slenderly known himself. (I.i.)

Regan identifies Lear’s fatal flaw: he lacks self-knowledge. Over the course of the play, Lear will develop genuine self-knowledge, but that knowledge won’t save him from the tragic fate he has set in motion.

You should be ruled and led
By some discretion that discerns your state
Better than you yourself. (II.ii.)

Regan tries to tell Lear that Lear does not see himself clearly. These lines develop an important question in King Lear: whether elderly men should continue to wield power, or pass their power on to the next generation.

Say if I do, the laws are mine, not thine.
Who can arraign me for’t? (V.ii.)

Goneril declares that as queen, she is above the law. King Lear asks what justice is and where it comes from: is the law simply whatever the monarch says it is? Justice was an important topic when Shakespeare was writing King Lear. King James I of England was especially interested in ideas surrounding justice and the law.