Scholars have long debated the influence of Milton's monism on Paradise Lost, but they have rarely discussed its impact on the text's gender politics or its implications for our understanding of how Milton portrays companionate marriage. Addressing this oversight, this essay argues that Milton's monism leads him to advocate for "monist marriage"—a marriage wherein couples unite both body and soul for "mutual help" towards spiritual advancement. This essay demonstrates how Milton presents marriage as an ongoing process by repeatedly depicting Adam and Eve moving hand-in-hand through Eden. Furthermore, given Milton's monist belief that body and soul are merely two terms for the same substance, it is possible to read Adam and Eve's unity as "one soul" in marriage as monist and, potentially, egalitarian. Yet Milton's incorporation of Saint Augustine's gendered concept of the soul within his monism sanctions the poet's misogyny by enabling a reading of Eve as necessarily subordinate to Adam. The final image of Adam and Eve exiting paradise hand-in-hand, however, encourages Milton's readers to envision a future for marriage predicated on true gender equality. The U.S. Supreme Court's recent use of companionate language to argue for same-sex marriage further demonstrates how companionate marriage ideals continue to disrupt marriage norms.