Out of the corner of his eye Gatsby saw that the blocks of the sidewalks really formed a ladder and mounted to a secret place above the trees-
Gatsby sees Daisy as his connection to the Upper Class lifestyle, or his “ladder” up the social hierarchy.
The life of luxury without burden, the one that Daisy and Tom live now, is Gatsby’s ultimate goal. Money is the most powerful thing in the world, and no earthly limits or rules can stop someone with a lot of it. The wealthy are inducted into this “secret place above the trees,” where they are higher than everything. Gatsby thinks if he can get to Daisy “alone,” meaning if Daisy did not choose to marry another man from her social circle, then he will be able to suck out of her the wealth that will support his dream.
Additionally, given that Gatsby views himself as a “son of God” who must be about his father’s business, he might have even higher aspirations here. If Gatsby were able to become rich and powerful he would view himself as somewhat of a demigod; so the ladder he is talking about might by his version of the “stairway to heaven”.
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