In Act 2, Scene 4, Regan and Goneril have conspired to deprive their father of his knights because they are afraid of how he might use the men against them and reclaim his authority as King. The old man finds himself being deprived of his prestige and reduced to the condition of an elderly dependent living on the charity of his two daughters. Goneril finally asks:
Hear me, my lord:
What need you five and twenty, ten, or five,
To follow in a house where twice so many
Have a command to tend you?
And Regan asks:
What need one?
Lear finds himself in the humiliating position of trying to explain why he feels the need for some superfluous show of his royal status. He says that if any human doesn't possess more than the barest necessities he is no better than an animal, and he reminds his daughter that as a woman she ought to understand that she needs more to wear than just something simple to cover her body; she needs adornment.
Lear than breaks off his explanation because he can't stand being in such a helpless state that he has to plead with his own daughters. He is saying, "But for true need--" and then he can't go on. He becomes more and more enraged until he finds himself abandoned by both daughters and their husbands and left out of doors with a storm coming on. This is the crux of the play: the king gives away his entire kingdom and then finds himself homeless because of the selfishness and ingratitude of his two daughters. He thought they loved him, but he finds out that they have no love for him at all.