Letter 107

Isidore of PelusiumUnknown|isidore pelusium
friendship
From: Isidore of Pelusium, monk at Pelusium
To: An unnamed recipient (addressed as "most gentle")
Date: ~410 AD
Context: Isidore explains how the devil operates — not through foreknowledge of thoughts but by reading the body's outward movements and impulses, then directing temptation accordingly.

The devil does not know what is in the mind, most gentle one. That is the exclusive power of the divine alone, which fashioned our hearts and searches them. But from the movements of the body, he hunts the soul's intentions.

Consider: if he sees someone looking around with curiosity, feasting his eyes on others' beauty — seizing that person's impulse, he immediately incites him to adultery or fornication. If he sees someone quick to anger and easily inflamed, he immediately sharpens the sword and urges him toward murder. If he sees someone greedy for shameful gain, he pushes toward robbery and theft.

This is how the enemy works: not from inside knowledge but from outside observation. He is not reading your soul; he is reading your body, your glance, your posture, your movements. From these he infers your current vulnerability and attacks there.

This is useful to know. It means that the discipline of the body — guarding the eyes, moderating speech, controlling the expression — is not merely external propriety. It is the concealment of what the devil would otherwise use against you. Those who discipline their outward conduct are denying him the information he needs.

Modern English rendering for readability. See the 19th-century translation or original Latin/Greek for scholarly use.