The soul can split the sky in two and let the face of God shine through.

The line imagines the human soul as possessing a disruptive, revelatory power: it can “split the sky,” breaking through the apparent ceiling of ordinary perception, and thereby allow a glimpse of ultimate reality (“the face of God”). Read this way, the image fuses mystical aspiration with a modern, almost violent metaphor of breakthrough—suggesting that transcendence is not passively received but actively forced open by inner intensity (love, grief, ecstasy, artistic vision). Even without a securely identified source, the phrasing is consistent with Millay’s frequent interest in heightened states of feeling and the way private emotion can take on cosmic scale.