The Heart asks Pleasure – first –

The Heart asks Pleasure – first – 
And then – excuse from Pain – 
And then – those little Anodynes
That deaden suffering – 

And then – to go to sleep – 
And then – if it should be
The will of its Inquisitor
The privilege to die –
                         F588 (1863)  J536

In a relentless series of "And then –", Dickinson charts the Heart's progression from desiring Pleasure to asking for the "privilege" of death. That's quite a deterioration in two stanzas. Other poets might offer an example or two, a descriptive phrase here and there, or at least a few adjectives and adverbs. But Dickinson strips the poem to the bones. 
        She writes it straight: Pleasure, Pain, Anodynes, sleep, death. Of those, she expands only on Anodynes: they are "little" in the way an aperitif or sleeping pill might be little. Yet such small things can "deaden suffering". This phrase not only foreshadows the final line, but makes the progression from the pain in the previous line quite clear. We first ask to be spared pain. When we aren't spared, we try to numb it.
        Sleep is a deeper anodyne. Yet sleep doesn't come easily to an unquiet mind and that which is granted by a pill is a dead sleep.  It is an easy step from there to desiring death. Dickinson may have been hearing Hamlet as she composed this poem: "To die, to sleep – /… and by sleep, to say we end / The heart-ache, and the thousand Natural shocks / That Flesh is heir to? 'Tis a consummation / Devoutly to be wished." [Hamlet Act 3, Scene 1). Hamlet continues, though, to say it is "the dread of something after death" that deters suicide. 

Tomas de Torquemado, Grand
Inquisitor of Spain, 1482-1498

        Because of this and, more specifically, the Calvinistic opinion that suicide is a grave sin, Dickinson adds a caveat to the desire for death: "if it should be / The will of its Inquisitor". She refers to God, and while his aspect as the Heart's Inquisitor might mean simply that he would be questioning her, the term is too loaded with negative connotations for Dickinson to have not intended them. Grand Inquisitors might well decide that a subject should be tortured or burned at the stake. 
        But the poem twists that ending. Here the heart, thwarted at every step, finally wishes to die; seeks the "privilege" of dying. It is the Inquisitor who has power and choice, not the speaker. He might withhold his permission – and that would be a form of torture.


A second reading of the poem might find Dickinson echoing a different Shakespearian passage altogether, that of Jaques' monologue in As You Like It where he lists the seven stages of man, from infant to decrepitude. In Dickinson's abbreviated version we begin as children wanting pleasure. We learn to avoid pain and then how to deaden it. We take to our beds and then ultimately welcome death.
This reading, though, seems too gentle for the stark terms of this poem with its thwarted heart and its dread Inquisitor who doesn't deal in happiness or relief, but only grants or withholds the final peace.