Blindness and sight
Lear cannot see which daughters love him. Gloucester literally cannot see after Cornwall blinds him. The play uses physical and emotional blindness together: both men have to lose their ability to see before they understand what was in front of them.
Power and its loss
Lear gives up his kingdom but expects to keep his authority. The play tracks what happens when that expectation collides with reality. Without power, Lear has no protection, no respect, and no shelter. The title means nothing once the land is gone.
Parents and children
Two father-child relationships drive the plot. Lear misjudges all three daughters. Gloucester misjudges both sons. The play puts bad parenting and bad children in the same frame, and shows how the damage runs in both directions.
Loyalty and betrayal
Kent and Cordelia stay loyal even after Lear punishes them for it. Edmund and Goneril and Regan betray the people who trusted them. The play keeps showing the gap between who deserves loyalty and who receives it.
Madness and clarity
As Lear loses his sanity, he starts to see things he could not see as a king. His madness strips away the performance of royalty and leaves something more honest. The play treats breakdown as a form of revelation, not just collapse.