Final answer:
The speaker of the quote is Adam from John Milton's 'Paradise Lost', discussing the single prohibition set by God amidst numerous freedoms.
Step-by-step explanation:
The speaker who says, "Then let us not think hard / One easy prohibition, who enjoy / Free leave so large to all things else, and choice / Unlimited of manifold delights," is Adam in John Milton's epic poem Paradise Lost. These lines express Adam's consideration of the relative ease of adhering to the single prohibition set by God despite the freedom they enjoy in the Garden of Eden. Such themes of free will, temptation, and the consequences of disobedience are central to this literary work.