St. Francis de Sales would look at the life of a mystic to discern whether or not they were being deceived by Satan.
St. Francis de Sales was skeptical of any person who claimed to have mystical visions or a deep spiritual life but were uncharitable toward their neighbor.
Pope Francis quotes the saint’s writings on the topic in his apostolic letter, Totum amoris est.
If you see a person who in prayer has raptures that exalt him above himself to God, and yet has no ecstasy of life, that is, he does not lead a life elevated and joined to God, above all by means of constant charity, believe me, Theotimus, all his raptures are exceedingly dubious and dangerous.
St. Francis de Sales goes even one step further, and claims that if a mystic does not lead a life of charity, their spiritual experiences could be from Satan himself.
Being above ourselves in prayer, but beneath ourselves in life and action, being angelic in meditation, but brutish in conversation, is a true sign that such raptures and ecstasies are nothing other than diversions and deceits of the evil spirit.
St. Francis de Sales’ words are a reminder to us all that while the spiritual life is important, it must be reflected in our works.
Our love of God naturally leads to a deeper love of our neighbor.