How do Christians discern genuine spiritual experiences from hallucinations or other mundane psychological phenomena?

I have had God speak to me. HE had the Holy Spirit prick my heart for a decade or so about forgiveness regarding a certain person. My answer was always the same, "how can I forgive her, she wont admit what she did?". Well when I was on my knees thanking God for how everything came together when I was ill, HE told me again to forgive. I gave my usual response. Then I --felt I guess you can say, it was not audible. But very clear. 5 life changing words. "How did I forgive you?". I cried & immediately forgave her in my heart. Later when I saw her, I went to her & gave her a hug. She felt it. She cried. It was very healing for me & remains so to this day. 5 life changing words. That's how God speaks.

How do Christians discern genuine spiritual experiences from hallucinations?

Let us recall that Joan of Arc was born circa 1412, and was burned at the stake in 1431, in fulfilment of the sentence passed by an ecclesiastical court convened by the English authorities in France. Her story is well known, and there are good biographical accounts of her life, mostly based upon the evidence given at the trials which led to her eventual death. Clearly such accounts are not impartial – but they are also extensive and detailed. Joan’s voices were interpreted at the time either as demonic or divine, according to the view that one chose to take. These views seem largely to have been politically determined. Much more recently, Joan has been canonised by the Roman Catholic Church, and at the same time has been diagnosed by various commentators as suffering from a psychiatric disorder. Her voices are thus ambiguous, although one can hardly fail to admire her courage of conviction in holding so faithfully to the truth of her experience despite such appalling consequences.

The relationships between hallucinations, spiritual experiences, voices, visions and revelations, are therefore not straightforward. Voices and visions may be of variable perceptual force and may or may not be strictly hallucinatory. Even if they are, this does not negate their spiritual significance and checklists of criteria for making a differential diagnosis between spiritual experience and mental illness are often both stigmatising and naïve. Reality is untidy, and often ambiguous, not least in matters of mental health and spirituality. Discernment is needed. Let wisdom be the guide.

How do Christians discern genuine spiritual experiences from hallucinations? Brianna Barkocy Deals with this in the following article : Madness or Mysticism: An Analysis of the Interpretation of Hearing Voices as an auditory Hallucination or Religious Experience The basic outline here will hold for other forms of hallucinations, such as visions. Note that they must not contradict Sacred Scriptures, a point already mentioned in Mike’s answer.

Coding Testimonies

To analyze these two testimonies, I created a coding rubric (Figure 1) based on the criteria delineated in the previous chapter as well as the official diagnostic criteria provided in the DSM-V. For each testimony, I marked each mention of voices which matched the criteria for religious experience according to my rubric as a 0 and each mention of voices which matched the criteria for psychosis as 1 to delineate between the two. I then counted the number of 1s vs number of 0s within each testimony. I also counted how many times voices were mentioned in total. I then compared the number of times the voices met criteria for psychosis and the times the voices met criteria for religious experience within each testimony.

Religious Voices

Source of Voices

• Voice distinctly different from own voice or intrusive thoughts

• Single voice

Incidence

• Irregular, inconsistent occurrence of voice

• Occurs in times of need, indecision, or social crisis

Content

• Provides direction

• Full sentences, complete phrases

• Relation to Scriptures

• Speaks specifically to the voice hearer

• Content includes one of the following: scriptural references, references to current events, issuing of commands, messages of consolation, offering of future direction, advice giving, expressions of love or deep emotional connection Tone

• Emphasis on hope or human dignity

• Positive and uplifting

Individual Response

• Contributes to the development of one of the following: peace, growth, humility, balance, free will, inclusiveness, and legitimacy

• Person retains a sense of control over the voices

Psychotic Voices

Source of Voices

• Voice distinctly different from own voice

• Can have one or more voices in conversation

Incidence

• Present for 1 month or longer or constant

• Occurs in the midst of every day events or after a traumatic experience

Content

• Offers critique or criticism

• Disjointed phrases, individual words, repeated phrases

• Speaks to the voice hearer, in third person or about the voice hearer

• Content includes one of the following: issuing of commands, echoing of patient’s thoughts, running commentary on everyday actions, or berating, cursing, threatening the individual Tone

• Negative and nagging

• Distressing

Individual Response

• Contributes to the development of one of the following: agitation, stagnation, inflation, preoccupation, compulsion, isolation and eccentricity

• Leads to self-harm or injury

• Individual feels helpless in the face of voices, lack of control

It almost seems from the preamble to your question that you are really asking two questions.

1. How can true prophetic visions or dreams be discerned from mundane dreams or hallucinations?
2. How can I answer skeptics regarding these issues?

I will start with the second of these, your preamble. After many years in the Christian life, and having been a skeptic myself years ago, I have come to realize that God may not be all that interested in convincing skeptics. I do not mean that God hates them (He doesn't), or considers them hopeless cases (He doesn't - I am proof of that, and thankful for it). But skeptics, almost by definition, have their minds and hearts set against the gospel or the reality of God.

Have you ever wondered, or been asked by a skeptic, Why does God not show His reality and His power openly, which would convince the entire world to worship Him alone?

There are multiple examples in the Scriptures to indicate that God reveals Himself primarily, perhaps exclusively, to those who seek Him.

Matthew 16

The Pharisees and Sadducees came to Jesus and tested him by asking him to show them a sign from heaven. He replied, "... A wicked and adulterous generation looks for a sign, but none will be given it except the sign of Jonah."

Revelation 3:20

Behold, I stand at the door and knock. If anyone hears My voice and opens the door, I will come in and dine with him, and he with Me.

And there is Paul's diatribe concerning the pagans of Rome in Romans 1:18-32:

... Furthermore, just as they did not think it worthwhile to retain the knowledge of God, so God gave them over to a depraved mind, so that they do what ought not to be done. They have become filled with every kind of wickedness, evil, greed and depravity....

To me these all seem to be reflections of Proverbs 3:34:

Though He [God] scoffs at the scoffers, He gives grace to the humble.

This Proverb is not obscure, it was quoted twice by the Apostles in their letters: James 4:6 and 1 Peter 5:5.

Even Paul's own conversion, due to the Lord's personal appearance to him in a vision, cannot in my opinion be considered an exception to this. As a persecutor, Paul still had a zeal in his heart for the God of Israel. He did not persecute in order to build up his own reputation or political power. Paul was misguided, and Jesus corrected him in spectacular fashion. After that, he described himself in his letters as "a prisoner of Jesus Christ", etc. and became one of those he once persecuted with equal zeal.

Beyond these matters internal to the heart, we have what might be considered a curious gospel passage. In Nazareth, the people knew Jesus and his family, and disbelieved. Matthew 13:58:

And he did not do many miracles there because of their lack of faith.

Mark 6 tells the same story. Why would unbelief prevent the doing of miracles? Perhaps that is the wrong question. Maybe it is not that unbelief nullifies the power of God. Maybe instead, unbelief is an impurity and a profanity of the heart, with which the pure and holy things of God cannot co-exist, being opposite each other. And maybe it is therefore a mercy of God that the pure and holy miracles are not done in that situation, because that would intensify the destruction of men's souls (Lamentations 3:23; Genesis 3:22).

Why would that be true? It occurs to me that when the Pharisees and Sadducees demanded a sign, they were, perhaps ignorantly, tempting God. And a skeptic who demands that God show His power, in order to believe that God even exists, certainly tempts God. But God does not serve us. God is not tempted, or mocked. Meaning, God does not respond to these things, unless with a just wrath. Were God to reward this tempting or mocking, it would empower those who tempt and mock. Just imagine what would follow - people demanding more and more 'proof' from God Almighty, in effect making God their servant, elevating themselves above God. Is that not Satan's ultimate goal? This cannot be!

Therefore, while we as Christian believers are missionaries to the entire world, and while God genuinely and deeply loves every one, and our words and actions should be reflections of that love at all times, still there is a spiritual reality at play when unbelief is involved. God does not, or possibly in a sense cannot, reward unbelief through miraculous things such as visions, healings, or manifestations. Nor, it seems, should we attempt to do so.

In my own personal experience, some of the dreams or visions that I have received, that I now believe to be from the Holy Spirit, have served as infallible proof to me of certain things, of a personal nature. But none have been of such a nature that could be used as evidence to convince a skeptic of anything at all. Incontrovertible proof to me, but just a story to anyone else. I think this is how God prefers to do things. He isn't interested in making a big show. Not until the Day of Judgement, that is. For the time being, He speaks in whispers to those who seek Him. There are healings, but these seem to happen for people who are seeking, not for skeptics (there could always be exceptions I suppose). And anyway skeptics are not generally convinced by such things.

Now to the second part of your question. How can one discern whether a dream, or a waking 'vision' experience, is a genuine message from the Holy Spirit or something else? I agree fully with @Mike's criteria, which I believe are summed up by 1 John 4:1:

Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world.

By "spirits" John does not mean 'ghosts'. This term can apply to teachings, ideas, feelings, urges, thoughts, dreams, even social trends. Clearly John is advising us to consult our God-given reason, and our understanding of the teachings of God.

I believe we would do well, if we believe we have had a prophetic experience, whether a waking vision or a dream, to consider carefully:

• Does the waking vision or dream contain any verifiable details that were not known to you beforehand? (Note: even if such details are confirmed, this should not necessarily be considered proof of authenticity! Pharaoh's magicians performed wonders.)
• Your own maturity level in your Christian walk. What wisdom can you bring to bear for discerning this?
• Whether you are firmly grounded in your doctrines and understanding. Someone with relatively weak understanding may misinterpret a real vision or dream, or mistake a mundane dream for a divine revelation.
• Certainly if receiving treatment for any mental illness in the neighborhood of schizophrenia or psychosis, this is serious grounds for doubt. Insanity is a state of captivity to demonic influences.
• If you had a fever at the time, this is grounds for doubt, but should not automatically disqualify.
• If you are a drug user (including certain prescriptions!) or alcohol abuser, this is grounds for doubt, but should not automatically disqualify. There are plenty of dramatic and miraculous salvation stories of people in situations like this.
• Depending on the subject matter at hand, do you have any kind of emotional over-investment in this area, that would logically lead to doubt?
• How is your prayer life doing?
• Is there any kind of moral failure in your life that still has a hold over you, in practical terms or because you have not yet repented? If so, this could be reason to doubt the veracity of a possible prophetic vision or dream.

These questions are relevant because you need to cleave as closely to God and His ways as possible in order to hear Him clearly and properly. Some of these questions are difficult to self-evaluate. Consult with an elder in the faith, whom you deeply trust, and who will not himself be skeptical of the concept or reality of prophetic visions and dreams. The question at hand is not whether God speaks through visions and dreams (He does), but whether He has spoken to you in this way.

Also keep in mind, many (not all) prophetic messages are given to multiple people (and sometimes NOT given directly to the intended recipient!) as a means of confirmation. Search for confirmations of this type.

And of course, and this should go without saying, pray and ask God for wisdom. Maybe fast over it.

"How do Christians make sure this is not the case? How do Christians discern genuine spiritual experiences from hallucinations or 'mind tricks' in general?"

The same way believers in every other religion know that theirs is the one truth: through faith, not reason.

Consider, for example, the case of Srinivasa Ramanujan, the Indian mathematics prodigy who with very little formal training produced mathematical formulas that baffled and astonished the best mathematicians in the world. When asked how he produced them, he responded that they were revealed to him by the Hindu Goddess Namagiri in dreams and visions. Obviously, there's no proof - a hallucination could be perfectly convincing, and even the feeling of certainty that goes with it could itself be hallucination. But if one experienced such a vision, revealing a formula that after many years of effort other mathematicians were finally able to prove true, wouldn't it be reasonable to believe its origin was genuinely divine?

The feeling that one's spiritual experiences and insights are of divine origin is a common narrative in many different religions. The insights revealed are often at odds with one another, but the descriptions of how it feels are remarkably uniform. It appears to be how humans are wired - in the same way all humans see the same optical illusions. That doesn't mean that the experience is untrue, though.

One way of looking at it is to consider that the divine guidance may be "built in" from the beginning. It is inherent in the way the universe works, which determines how intelligence works, which is wired in to every human from birth. The answers and the certainty are already there inside you, you only have to listen. It may be both a hallucination and of divine origin.

You have to judge the veracity of such experiences the same way you do any other experience. Reason plays a part, but it cannot be sufficient on its own. 'Solipsism' is the philosophy that the entire universe we perceive is an illusion, and it cannot be disproved by any line of reasoning. The world we live in could be a dream, or a virtual reality computer simulation, or the work of an evil demon, inventing false experiences and feeding them to our senses. Any evidence or argument we can think of for its reality could be invented too. Indeed, we cannot even be certain that our methods of reasoning or our memory are reliable, either! How do we know that the entire world or our entire memory of the past is not a hallucination?

We make a leap of faith. We choose to believe, because we can't operate without the belief. We believe because whether it is true or not, our future experiences will probably develop as if it were true, and it's the best guide we've got. We believe because it brings us happiness, or comfort, or the assurance that our life is not empty and meaningless. We believe because we seem to experience the reality of it directly; because we are hardwired to believe what we sense. We believe in whatever we each believe for the same reasons and by the same means an atheist believes the world is real. How can he be sure his experience of reality is not an illusion? He can't. He simply has to take it on faith.

At the same time, we are all perfectly well aware that humans are fallible, and that history is full-to-the-brim with false religions that their adherents believed in as faithfully and with as much certainty as we do. Even the history of Christianity is filled with heresies and schisms, all of them sincerely held and fought for. Just as scientists are perfectly aware that scientific history is full of false theories and beliefs that were later disproved, and scientific controversies exist in which scientists today still dispute what is to be held true right now, and that they are no less fallible and imperfect than their predecessors. Nevertheless, scientists hold a working belief that their current theories are true, until proven otherwise, because absolute certainty is impossible and they would never be able to make any progress at all if they didn't. Our understanding of the world is imperfect. We all just have to do the best we can.

I think a case other answers haven't addressed yet is that of spiritual experiences which are overtly miraculous, i.e., that the experience cannot reasonably be attributed to a psychological phenomenon or random chance.

For example, a word of knowledge is a spontaneous 'download' of previously unknown information the person receives through an audible voice, a voice in their head, a vision, a sudden 'inner knowing', etc., which can be empirically tested against reality. If a word of knowledge is genuine, the revealed knowledge will prove to be accurate.

A very illustrative example of this extraordinary experience can be found in Ken Gaub's book God's Got Your Number (amazon link). I'm specifically talking about this story, excerpts of which are quoted below:

I was driving on I-75 near Dayton, Ohio, with my wife and children.
[...]
Suddenly the impatient ringing of a telephone nearby jarred me out of my doldrums. It was coming from a phone booth at a service station on the corner. Was no one going to answer this phone? Traffic noise from the busy intersection must have drowned out the sound, because the service station attendant continued looking after his customers, oblivious to the incessant ringing.
[...]
The operator said, “Long distance call for Ken Gaub.” I almost choked on a piece of ice. My eyes must have widened considerably. Swallowing hard, I said, “You’re crazy!” Then, realizing I shouldn’t be speaking to the operator like that, I said, “This can’t be! I was walking down the road, not bothering anybody, the phone was ringing . . .”
[...]
I listened dumbfounded as the strange voice introduced herself. “I’m Millie, from Harrisburg, Pennsylvania. You don’t k now me, Mr. Gaub, but I’m desperate. Please help me.”
“What can I do for you?” I asked. She began weeping. Finally she regained control and continued. “I was about to commit suicide. I had just finished writing a note, and I began to pray and tell God I really didn’t want to do this. Then I suddenly remembered seeing you on television and thought if I could just talk to you, you could help me. I knew that was impossible because I didn’t know how to reach you. I didn’t even know anyone who could help me find you. Then some numbers came to my mind and I scribbled them down.”
[...]
Knowing this encounter could have been arranged only by God, I began to talk to her and counsel her. As she told me of her despair and frustration, the presence of the Holy Spirit flooded the phone booth and gave me words of wisdom beyond my own ability. In a matter of moments she prayed the sinner’s prayer and met the One who would lead her out of her situation and into a new life. I walked away from that telephone booth with an electrifying sense of our Heavenly Father’s concern and love for each of His children. What were the astronomical odds of this happening without God? With all the millions of phones and innumerable combinations of numbers, only an all-knowing God could have caused Millie in Harrisburg, Pennsylvania, to call that number in that phone booth in that particular moment of time.
[...]

Other examples of extraordinary spiritual experiences can be found in the following questions:

• Are there any accounts of "words of knowledge" taking place outside of Pentecostal and Charismatic denominations?
• Are there any documented cases of Xenoglossy (i.e. "Acts 2:1-13 type" tongues, understood by a foreigner) in recent history (19th century on)?
• Do Cessationists reject Lee Strobel and Craig S. Keener's books collating modern-day miracle reports?

The entirety of the book of Job (1) is an account of a man who, though a perfect man among his peers, and in regard to his own conscience, yet was deeply exercised within himself and feared one thing above all - which, in time, came upon him :

I was not in safety, neither had I rest, neither was I quiet; yet trouble came. [Job 3:25 KJV.]

Adversity came upon him and he knew not why. And his previous uncertainty was exposed, for, despite his religion, there were deep matters of soul not (yet) resolved within him. He had not (yet) entered into rest, by faith.

What did he really know of God ? 'Lo, he goeth by me and I see him not', Job 9:11.

Job's deep exercises of soul are laid bare for us as he questions within himself (even as his three friends, unhelpfully, criticise him, unfairly) what he really has experienced, what he truly has found of God, or not.

Thus a period of self-examination began in which he was tried as to his own integrity and, more importantly, as to wherein his trust lay : in self-righteousness and his own abilities or in the absolute rightness of God himself.

We see many like exercises of soul with the psalmists, David in particular but not only David, as to their true knowledge of God and we see how eager were these writers of spiritual experience to not rest in outward works, communal religion, their own religious practices : but they yearned for the real presence of the living God.

Unto thee will I cry, O LORD my rock; be not silent to me: lest, if thou be silent to me, I become like them that go down into the pit. [Psalm 28:1 KJV]

They craved the real presence of God within their own souls : his true person and the communion with Him that brings peace of spirit.

They did not wish to be left with an outward religion, with that which was exterior and that which was external to their inward person.

Consider how I love thy precepts: quicken me, O LORD, according to thy lovingkindness. [Psalm 119:159 KJV]

This we see also in the writings of the New Testament.

Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates? [2 Corinthians 13:5 KJV]

Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall: [2 Peter 1:10 KJV]

Both Paul and Peter exhort self-examination in order that we should not be left with a superficial and outward religion, bereft of the real experience of God himself, known through Jesus Christ, by the ministrations and the operations of the Divine Holy Spirit.

Also, the Revelation of Jesus Christ which God gave to him and which he, in turn, gave to John in Patmos begins, not with predictions of the future on earth, but begins with close examination of the real spiritual state of those within the Church.

For judgment must begin at the house of God, 1 Peter 4:17.

And the very first church addressed is commanded to examine themselves as to their first love.

Their patience, their faith, their trying of others, their fortitude, their hatred of bad doctrine : none is in doubt and all is recognised by he whose eyes are as a flame of fire, Revelation 2:1-7.

But what of their own hearts ?

What of their initial relationship with Jesus, the Son of man, Himself ?

Where is their first love ?

Yes, indeed, when, as the OP clearly states, we appeal to our own private experience in order to testify to our own personal faith, do we do so in confidence that we have not been deluded by tricks that have been played on us ?

Is our faith real ?

Is it truly founded upon a Rock ?

(1) I have put all of the discourses of the book of Job into verse form (850 verses) in order to aid assimilation of the book. The poetry entitled 'The Patience of Job' is available, free of charge and free of any registration, as a PDF download on my website.

A Christian who is suffering from an hallucination which they take to be a genuine spiritual experience will never discern it to be false, at the time. But once soundness of mind returns to them, then they might see it differently. This happened to a Christian friend of mine who had had years of mental health treatment prior to becoming a Christian.

She phoned me in excitement one day, saying she thought she had been given the spiritual gift of speaking in tongues. But she did not mean speaking in a language other than her native tongue - she meant babbling lots of strange sounds / words. I visited her and over several visits I was none the wiser as this came over her spontaneously, but I was never around when it did. Knowing what her mental health condition was, I had doubts about this being a gift of the Holy Spirit but said nothing as this was her own private, personal experience.

Well, a few weeks later, she told me she had learned from a medical professional person that it was a medical condition, and had accepted it as such. I noted that her mental state then was more calm than it had been a few weeks previously. She felt disappointed at the realisation, but accepted it and moved on.

I give this example to show that I could not discern whether my friend's claim was genuine or not, nor would I judge her. After all, I only had her word for it, and had never heard her making these strange utterances. But I recite it to also show that this Christian came to realise that she had not had a genuine spiritual experience after all. No doubt she had prayed a lot about it (and so had I), and when her mental state had stabilised, she thought rationally and came to see the experience differently. Such an episode never occurred to her again, as far as I know. As this is an anecdote, I now add more objective points.

Hallucinations are associated with certain drugs, particularly abuse of drugs. There can also be alcoholic hallucinations. Even certain foods can prompt hallucinations due to particular chemical reactions in the brain. From the 1960s onward there was an explosion of mystical experiences claimed by followers of certain spiritual leaders. These were rarely Christian leaders, but if drugs and/or alcohol were involved, Christian leaders or not, the effects were invariably doing things that the Bible warns against - sexual promiscuity being a prominent one. Without any further ado, a Christian would know that such an experience leading to sexual immorality, was absolutely never of God. But other give-aways would be speaking with a foul mouth, obscene language or gestures, lying, abandoning one's responsibilities, stealing, accepting every other religion or anti-Christian spiritual belief as on a par with what Jesus stated and did - that sort of thing. Basic bible knowledge would rule out a whole raft of claimed spiritual experiences.

A process of elimination should be employed in the first instance, with respect to any personal experience, then if all remains well, checking if it squares positively with what Christians know they are to do, and to stand for. But if the claimed experience is that of another, we can only observe from a distance and hold our peace, unless we are a Christian leader in a congregation that might suffer from deception via an hallucinating person in the midst.

However, if the spiritual experience is not an hallucination but a demonic trick, then the person is in deep spiritual trouble and will need help from mature Christians. I know of such instances, but not personally. Christians should know that they are warned in the Bible that a satanic influence can appear as an 'angel of light' (2 Cor.11:14; Gal.1:8; Rev.13:13-14). A Christian's safeguard from that is to utilise the full symbolic 'armour of God' as detailed in Eph.6:10-18.

But I'm always wary of people appealing to their own personal experiences to bolster claims about their faith. And if that is done in context of trying to prove that their own denomination is "the truth" (the unspoken implication being that different denominations are not) then I discount them. The truth is found in the person of Jesus Christ, and all Christians should look only to him, for he is the Way, the Truth and the Life (John 14:6). That's all any Christian needs.