Sound reason

What you call sound reason we Christians take to be a reason so infirm, so darkened and so far gone astray, that there can be no healing for it except by cutting off, with the sword of faith, and renouncing all the learning that has gone into its formation. If we take it for a sound reason, basing ourselves on a foundation that is uncertain, tottering, indefinite, constantly changing -- then it, being sound, will renounce Christ too.
St. Ignatius (Brianchaninov)