In the opening stanza of "The Brain- is wider than the Sky-", Dickinson contrasts the human brain with the sky. In the first line Dickinson sets the tone of the poem and states, "The Brain - is wider thean the sky-". I usually view the wide sky as being almost limitless, but here Dickinson is saying that the brain is even beyond the limits of the sky. In the second line, "for- put them side by side-", Dickinson asks the reader to compare the brain with the sky. In the third line of the first stanza, she says, "The one the other will contain", and without saying which one contains the other she leaves the reader to assume that the sky fits within the brain. The brain is able to incorporate the sky and the entire universe into it's thoughts. In the last line of this stanza, Dickinson writes, "With ease- and You- beside-", to strengthen the point. In this line "You" means the human body, which is ironic as the brain is physically smaller than the body, but not metaphorically.
In the second stanza of the poem, Dickinson compares the brain with the sea. In the 5th line of the poem, "The Brain is deeper than the sea-", Dickinson uses this metaphor to say that although the sea is made up of a vast amount of water, the brain can store an immense amount of knowledge. In the second line of this stanza, when she says, "for-hold them- Blue to Blue-", she may be reestablishing