Teresa of Avila, answered from the texts and cited to the page.
They can be trusted, but not on the strength of their sweetness, and not on a woman's word alone. By their fruits, and by the judgment of someone who can give light. First the tests, because I wrote whole chapters to give them. What the understanding fashions for itself is indistinct and fantastic, and we can turn our attention from it as we can fall silent when we are speaking; the divine locution cannot be put aside so.1
And there is a test more decisive still: the words the understanding forms effect nothing, but when our Lord speaks it is at once word and work. Even a word of reproof settles the soul, strengthens it, gives it light, and takes away dryness and disquiet as if by the action of a hand.2 The devil can counterfeit words, since he is wily, but he can never counterfeit the effects; he leaves neither peace nor light in the soul, only anxiety and confusion.3
And the surest mark is what the favour does to the one who receives it. If she rates herself more highly in consequence, it did not come from the Holy Spirit. When it is divine, the greater the favours, the less the soul esteems itself, and the more keenly she remembers her sins.4 As to who judges: not the soul herself. Imaginary visions are the most doubtful, and no one should desire them.
But if they continue, if the soul gains from them, if they lead to deeper humility and agree with the teaching of the Church, there is no reason to flee them. Even so, no one ought to rely on her own judgment; she must make everything known to him who can give light. That is the universal remedy, with hope in God, who will not let a soul lie in delusion if it is humble enough to yield obedience to the opinion of others.5
I did so myself. I told those who had charge of me that although I believed it was certainly God, I would do nothing at all unless it seemed to them more to the service of our Lord, and I kept nothing silent.6 Now, I will not pretend the two sit easily together. When confessors told me these words were fancies, and events turned so that their fulfilment seemed impossible, there remained a spark of certainty in my mind, I know not whence, that I could not quench though I wished to.7
So I obey in what I do, and I do not lie to myself about what I have seen. A learned man who has not tasted these things judges from outside, and I would sooner be judged by him than by myself, but I will not tell him I was asleep. And no one should condemn the favours because the person who receives them is not perfect. Who will set bounds to the goodness of our Lord? These graces are given not for merit, but to one because she is weaker, and they do not make anyone holy.8
What God gives in prayer is known by its fruits, not by its sweetness: peace, humility, the desire to suffer, love of neighbour, and the impossibility of doubting while it lasts. A locution that comes from God is distinct, remembered, effective and fulfilled; the imagination's is dim and goes; the devil's leaves disquiet. These things must be submitted to learned confessors, and she submitted them to a dozen; but a confessor who has not experienced cannot judge what he has not seen, and she will obey him in act while telling him he is wrong.910 The soul knows that it was God as a man knows he was not asleep.111213
It is in our power to turn away our attention from these locutions of our own, just as we can be silent when we are speaking; but, with respect to the former, that cannot be done.The Life of St. Teresa of Jesus
The words formed by the understanding effect nothing; but, when our Lord speaks, it is at once word and workThe Life of St. Teresa of Jesus
Satan could never counterfeit the effects I spoke of; he leaves neither peace nor light in the soul, only anxiety and confusion.The Interior Castle, or The Mansions
unless self-abasement increases with God's expressions of love, they do not come from the Holy Spirit.The Interior Castle, or The Mansions
no one ought to rely on his own judgment herein; he should make everything known to him who can give him light. That is the universal remedyThe Life of St. Teresa of Jesus
although I believe that it is certainly God, I would do nothing at all, for anything, unless it seemed to the one who has charge of me that it is more to the service of our LordSpiritual Testimonies, Relaciones I-LXVII
there yet remains so lively a spark of certainty in the mind (I know not whence it comes) that, although all other hopes die out, it cannot, if it would, quench this ardent spark of confidence.The Interior Castle, or The Mansions
Who will set bounds to the goodness of our Lord?--especially when these graces are given, not for merit, nor because one is stronger; on the contrary, they are given to one because he is weakerThe Life of St. Teresa of Jesus
I do not know if it be so but even this very day I thought it possible. I know by experience in many ways, when these locutions come from God. I have been told things two or three years beforehand, which have all come to pass; and in none of them have I been hitherto deceived. There are also other things in which the Spirit of God may be clearly traced, as I shall relate by and by. 4.The Life of St. Teresa of Jesus
For this reason these things are not for writing or saying, because it is impossible to understand them except for one who has experienced it, I mean to what extent this pain reaches, for the pains of the spirit are very different from those here. From this I gather how much more the souls suffer in hell and purgatory than can be understood here by these bodily pains.Spiritual Testimonies, Relaciones I-LXVII
Justly, therefore, does their hearer rejoice, when, after a thousand delays and enormous difficulties, they are accomplished. Although this success may entail great suffering on herself, yet she prefers it to the nonfuliilment of what she knows our Lord most certainly foretold. Possibly every one is not so weak as this, if indeed it is a weakness, though I cannot myself condemn it as an evil. 16.The Interior Castle, or The Mansions
Our Lord will reassure our confessor, whom, when He so chooses. He will inspire with faith that these locutions are from the Holy Ghost. 1 ' If not, we are freed from all further obligations in the matter. I think it would be very dangerous to act against our confessor's advice, and to prefer our own opinions in such a matter.The Interior Castle, or The Mansions
And if it be not a soul much exercised in prayer, it will find it enough to understand its state, be the books ever so clear. 11. I wish much that our Lord would help me to describe the effects on the soul of these things, now that they begin to be supernatural, so that men might know by these effects whether they come from the Spirit of God.The Life of St. Teresa of Jesus
The question the Inquisition put to her and every reader puts since; the texts hold both the submission and the certainty, and the modern scholarship reads the first as the price of saying the second.