Proving the immortality of the soul was a common challenge for the religious metaphysical writers of the seventeenth century. One attractive line of argument was premised on the ‘unity,’ ‘simplicity,’ or ‘indivisibility’ of consciousness (‘mind,’ or ‘soul’). While the religious issue of the soul's immortality dropped to a lower place on the philosophical agenda in the eighteenth century, the question of the unity of consciousness continued to run high as philosophers attempted to apply material atomism to mind and to vital phenomena in general.