"'Lear, Kent, Fool'"

The three characters from Shakespeare's King Lear who are present in the 'heath scene':

King Lear, who descends into madness during the course of the play;

The Earl of Kent, a character sympathetic to King Lear, who is disguised as Caius throughout most of the play;

The Fool, a supposed simpleton who, like most of Shakespeare's 'fools', is actually extremely astute.