Hughes tells us that Milton's thinking of Plato and that the Elder Brother is referring to the platonic theory that the noble spirit is released from the body after death.

休斯告诉我们，弥尔顿引用了柏拉图的东西,大哥用的是柏拉图的理论,人死后，高尚的灵魂将从身体释放出来。

耶鲁公开课 - 弥尔顿课程节选