The reason why the juniors are enjoined not to keep back any of their thoughts from the senior.
By these practices, then, they hasten to impress and instruct those whom they are training with the alphabet, as it were, and first syllables in the direction of perfection, as they can clearly see by these whether they are grounded in a false and imaginary or in a true humility. And, that they may easily arrive at this, they are next taught not to conceal by a false shame any itching thoughts in their hearts, but, as soon as ever such arise, to lay them bare to the senior, and, in forming a judgment about them, not to trust anything to their own discretion, but to take it on trust that that is good or bad which is considered and pronounced so by the examination of the senior. Thus it results that our cunning adversary cannot in any way circumvent a young and inexperienced monk, or get the better of his ignorance, or by any craft deceive one whom he sees to be protected not by his own discretion but by that of his senior, and who cannot be persuaded to hide from his senior those suggestions of his which like fiery darts he has shot into his heart; since the devil, subtle as he is, cannot ruin or destroy a junior unless he has enticed him either through pride or through shame to conceal his thoughts. For they lay it down as an universal and clear proof that a thought is from the devil if we are ashamed to disclose it to the senior. 763
Compare the Conferences, Book II. c. x., where Cassian returns to the same subject. A similar rule that the brethren are to lay bare all the secrets of their hearts to their superior is given, by S. Basil in the Longer Monastic Rules, Q. xxvi., and in the Rule of S. Isaiah (cc. vi., xliii.), printed in Holstens Codex Regularum, Vol. I.