Lear is negotiating his accommodations with his daughters and it is not going well. The Fool taunts Lear by saying that Regan will be kind where Goneril was not:
Shalt see thy other daughter will use thee kindly;
for though she's as like this [kindliness] as a crab's like an
He then reverses his message and says what Regan will be like as opposed to what she will not be like:
She will taste as like this [Goneril] as a crab does to a
The following riddle is a lead in to his next jibe at Lear's senseless choices:
Thou canst tell why one's nose stands i'
the middle on's face?
[...]Why ... that
what a man cannot smell out, he may spy into.
In other words, Lear is being jeered for not knowing the truth about his daughters: he should see the truth or at least smell out foul deeds in the wind.
I have to agree that the fool is warning Lear. He is making a point of showing Lear that some things are exactly as they seem (instead of how they appear). Many of Shakespeare's plays were full of...
(The entire section contains 6 answers and 605 words.)