Evil spirits distract us
And there is no question but those evil spirits, who are continually seeking whom they may devour (1 Peter 5:8), make use of all the foregoing occasions to hurry and distract our minds. Sometimes by one, sometimes by another of these means, they will harass and perplex us, and, so far as God permits, interrupt our thoughts, particularly when they are engaged on the best subjects. Nor is this at all strange: they well understand the very springs of thought, and know on which of the bodily organs the imagination, the understanding, and every other faculty of the mind more immediately depends. And hereby they know how by affecting those organs to affect the operations dependent on them. Add to this that they can inject a thousand thoughts without any of the preceding means, it being as natural for spirit to act upon spirit as for matter to act upon matter. These things being considered, we cannot wonder that our thought so often wanders from any point which we have in view.
1771 text
9. *And there is no question but those evil spirits, who are continually seeking whom they may devour, make use of all the foregoing occasions, to hurry and distract our minds. Sometimes by one, sometimes by another of these means, they will harass and perplex us, and so far as God permits, interrupt our thoughts, particularly when they are engaged on the best subjects. Nor is this at all strange: they well understand the very springs of thought, and know on which of the bodily organs, the imagination, the understanding, and every other faculty of the mind more immediately depends. And hereby they know, how by affecting those organs, to affect the operations dependent on them. Add to this, that they can inject a thousand thoughts, without any of the preceding means: it being as natural for spirit to act upon spirit, as for matter to act upon matter. These things being considered, we cannot admire, that our thought so often wanders from any point which we have in view.