The so-called "interaction problem" of spiritual/physical

In discussions with materialists here over the years, I’ve run into an assertion they make which (they think) is a real “gotcha!” moment for believers. “If the divine actually does interact with the physical, then clearly you would have empirical evidence (albeit secondary) of the spiritual realm. You don’t… therefore, the spiritual realm does not exist! QED!”

I’d like to raise this topic for discussion. What do you think? Do you agree? Disagree? Want to propose a different framework for the discussion?

However, this argument seems short-sighted on two counts:

  • First, what I’ll call the “sighting the invisible man” problem
  • Second, something I’ll label “the problem of merely physical artifacts”

(If there are standard terms for these in the literature, please let me know!)

In this post, I’ll tackle the first issue. If there’s interest, I’ll raise the second one in a subsequent post.

The first problem speaks directly to the materialist’s claim: if there really were spiritual beings who interacted with us, we’d be able to document these interactions, and since there is no documentation as such, then the claim is false. That seems short-sighted for a couple of reasons:

  • inability to predict a-priori when these interactions will occur
  • inability to predict what form these interactions will take (such that we might be prepared to measure them empirically)

Neither of these go to the materialist’s desired conclusion of “therefore it doesn’t exist”; rather, it just shows “we cannot reasonably hope to detect it a priori or measure it.”

Here’s the thought experiment: let’s suppose that you wish to prove to me that there’s an invisible man who exists. I ask you to prove it. (Let’s presume he’s smart enough not to walk into cloud of talcum powder or leave footprints on flour spilled on the floor.). At every point at which you attempt to prove his existence, I say “a-ha! no proof! Therefore, he doesn’t exist!”

And yet, the failure to provide empirical evidence doesn’t proceed from the non-existence of the phenomenon. Rather, it proceeds from the impossibility of predicting the occurrence. Every scientist knows that, if a valid hypothesis cannot be formed, there is no conclusion that can be reached! Yet, it seems that materialists want to say “absence of evidence is evidence of absence.”

What do you think?


I would make the counterclaim that miraculous events can and have left very clear evidence.

Take, for example, a miraculous healing. Stage 4 cancer, doctors call it inoperable, incurable. The patient is given weeks to live, if that long. And yet, somehow the cancer vanishes, practically overnight. There are no ill effects, its like it was never there to begin with.

There are dozens, if not hundreds, of cases just like this. Cases which have no rational explanation given everything we know about biology, medicine, and cancer.

That, to me, is the fingerprint of spiritual interaction. It could not be clearer. All the miracles that have happened at Lourdes, thousands upon thousands of healings which have no clear explanation. (To be fair, fewer than a hundred have been officially pronounced as miracles, but that number is dwarfed by the literal thousands which have been put forward as miracles. Still, 68 at last count, that’s nothing to scoff at.) Eucharistic miracles offer more evidence of the spiritual interacting with the physical. The evidence exists for anyone willing to actually examine the findings.

To answer the core question though, I see no reason to conclude that an interaction must leave evidence. Spiritual beings are by definition non-physical. There’s no reason to assume that a non-physical entity interacting with a physical entity would leave evidence that a physical entity could discern. The claim that it would is a baseless assertion.


There’s still the “invisible man” objection – we cannot predict these occurrences, so we cannot measure what they see as “putative interaction.”

Yet, the real problem here is the second issue – the “problem of merely physical artifacts”.

Materialists want to assert that there is nothing but the physical and empirically measurable, and demand empirical evidence for supernatural events. However, as you point out, all you’re left with is a physical artifact – a healed person, etc, etc. You call this a “fingerprint of spiritual interaction”. However, a materialist will look at this and retort “I don’t see any ‘imprint’ of the spiritual; all I see is a healed person.”

The problem is that, no matter what empirical evidence is produced, they always can shrug and say “it’s just empirical evidence; it doesn’t demonstrate the supernatural”. Or, perhaps, “ok… that was unlikely, but not impossible”. Or, even, “you cannot conflate the ‘unexplained’ with the ‘supernatural’!”

To my mind, the request for empirical evidence of non-physical beings and interactions is simply acting in bad faith. Materialists – and we believers! – should recognize that this is a demand for the wrong tool in the wrong job. Far from proving their assertion, it merely shows a lack of insight, at best, and a particular brand of “dirty pool” at worst.


I am a firm believer of spiritual reality I have to say that physics is an approximation of reality. There is no theory which can predict reality until the last digit. Spiritual beings can stay invisible if they act in the windows of error bar of our apparatus and don’t violate laws of physics.

I agree completely. I was just presenting my counterpoint. I’ve used it before and, to my knowledge, it’s never once convinced a materialist. There’s always the assertion that “The apparent miracle was natural, we just don’t know how yet. We will one day.” It doesn’t matter how blatant the miracle is (like literal bread turning into literal heart muscle), a dedicated materialist will always find a dodge.

That’s why I’m a great fan of the saying “i don’t have enough faith to be an atheist.” :stuck_out_tongue:


It was documented- in the most widely published book of all time…

1 Like

Are we speaking of just miraculously phenomena and intervention in the natural order? Classical arguments make the case that there wouldn’t be a natural order without the divine.



Yes! In the absence of empirical evidence, there is eyewitness evidence! And yet, the responses are always the same:

  • I don’t believe God was involved in the inspiration of the Bible
  • I don’t believe that those things actually happened
  • The accounts themselves are spurious / inaccurate / doctored-up

There’s really no “winning solution” here. What they demand is unreasonable to expect. What we produce is unacceptable to them.

And then they call us irrational! :rofl:

To a materialist, there is no “divine order.” Its existence is what they ask us to demonstrate empirically…


No one is making them believe anything. Does it matter that they don’t support your beliefs? If so, why?

Your assumption of the materialist’s claim is incorrect (as usual!). It is: Because there are no positive outcomes, it is rational to doubt the claim about the supernatural. Millions and billions of tests are conducted every minute, every day! Some of them seem to have a positive outcome, but none of them are conducted in a well-designed, double-blind method.

I can predict the outcome with a huge probability. There will be NO positive outcome. None whatsoever. Once in a blue moon there will be a seemingly positive outcome, and that is all.

What kind of prediction can you offer?

First, there is no properly designed double-blind experiments for ANY miracles. It is always an a-posteriori claim of something that MIGHT have happened.

There were no REALLY miraculous events, things that are contradicted by the known physical laws of the universe. For example the stars rearranging themselves to display the texts in the Bible on the sky. Medical “miracles” are spurious. Physical “miracles” do not exist.

Yeah, this is exactly what we’re talking about. It doesn’t matter how blatantly obvious the miracle is, if you’re unwilling to admit the possibility of the miraculous you will discard any amount of evidence to avoid facing the hard truth.

There have been multiple studies performed on Eucharistic miracles concluding that the samples were human heart tissue.

The True Presence: Eucharistic Miracles Over the Centuries for Corpus Christi

The Amazing Science of Recent Eucharistic Miracles: A Message from Heaven? 

The Eucharistic Miracles of the World (Not a scientific paper, just an list of known miracles)

That’s a bold assertion, one which you cannot prove by your own metrics. There is substantial evidence for miracles, as previously noted. However, as we were saying, you appear to be of the type for whom no evidence would be sufficient. You have made up your mind, all purported miracles can be dismissed, even if that dismissal is as simple as “such things don’t happen.”

1 Like

Not true, and I even gave an example of a possible miracle, which would be accepted. There are some basic principles in the universe and if there would be an event what would contradict them, that would qualify as a bona-fide miracle. The principle of preservation of matter/energy and the like. The speed of light in vacuum. The temperature below zero Kelvin… Changing the properties of metals so they will NOT conduct electricity and changing the properties of insulating materials, so they will start conducting electricity… and so on.

None of the so-called miracles - Eucharistic miracles - were performed in a properly designed, double blind fashion. Not some measly medical miracles either. Not even the regeneration of a lost limb would qualify, because we are aware of spontaneous regeneration in other animals.

Your suggested miracles are not rejected on principle, rather because there is no sufficient evidence for them.

This tells me you’ve never actually read the studies that were done, because they were, or at least as close as you can get. Double blind doesn’t really apply here, as there’s not a control group of fake Eucharistic miracles that’s being tested against. Double blind is useful for medical experiments, where you can have one group taking the real medicine and another taking a placebo. I find it funny when people demand double blind tests for everything given that double blind really only applies for a limited scope of experimentation.

The participating examiners were given a sample of the miraculous flesh and not told where it came from. That’s as close to double blind as you can get in this type of study. Multiple examiners all independently verified that it was human heart flesh, type AB. These findings were later confirmed by the WHO. This is one of… I think we’re up to three such miracles that have been studied in this manner. It is incontrovertible evidence, unless you want to believe that all the scientists independently chose to lie about a sample they in no way knew was supposed to be special, and that they further all arrived at the same falsehood completely independently of each other.

You are demanding miracles on your terms and severely limiting the scope of what you’ll accept. From the standpoint of seeking Truth, that’s just plain stupid. You entirely discount the massive, MASSIVE number of medical miracles that have been scientifically cataloged in the last century alone, let alone all the reported miracles in the whole history of The Church. You call them spurious when they are anyhting but.

The miracles from Lourdes, for example, are all minutely detailed, with full medical workups being run and the before and after being compared. That’s why there are only 68 confirmed miracles out of literally thousands of reported miracles. If there is any room for a natural explanation they are not counted in the number. The only reason you disregard these is because, were you to admit of these miracles as potential evidence, they would provide overwhelming proof for the existence of miraculous occurrences.

And, of course you disregard the possibility that there was no error, cheating or practical joke involved.

Yes, I am interested in some miracles which could NOT be faked, or the result of some error, intentional or otherwise. This might be a surprise to you, but the only experts, whose opinion counts are the stage magicians, who are the masters of flimm-flammery, cheating and misdirection. If they can be convinced. that would be a serious argument for a miracle.

But everyday scientists or physicians are just as gullible as any random person from the street.

When I read the details about the miracle which earned the sainthood for JPII, I was very disappointed. Even assuming that the healing of the aneurysm was real, what kind of evidence could substantiate that it was JPII whose intercession produced the positive result? Is that the kind of “evidence” is enough to declare something a miraculous intercession? Sorry, that does not fly.

I discount the possibility of error because of the number of different eyes that examined it, as well as the substantial follow up investigation.

I discount the possibility of cheating because there is little to be gained by it, as non-believer such as yourself tend to discount it outright. I also believe the men who reported it to be of sufficient moral character not to cheat on something which is so deeply important to us.

I discount the possibility of practical joke because serious Catholics are not prone to blasphemy, and this would definitely be a blasphemy of one sort or another.

In all, I also weigh it against the abundant reports of these types of miracles throughout history, and it seems far more probable that they do occur than that they don’t.

Once again, you are only proving our point. I know you can’t see that, but its really quite sad to see, especially the contempt you seem to have for people who believe. No matter what, no matter how clear the evidence is (Because, again, the evidence in the miracles at Lourdes is undeniably clear. At least it is undeniable by anyone who actually examines the reports without the inbuilt assumption that miracles are false no matter what.), you will never accept it because it could always be a mistake, even if the methodology is rigorous and foolproof. By that same metric you should accept nothing, because no matter how solid our understanding of the physical universe it today, tomorrow it could be shown to be wrong.

The question of if it was JPII’s intercession which resulted in the miracle is a matter of faith. The fact that the aneurysm disappeared is a matter of science. It is all clearly documented. There are before and after scans showing it existing, and then not existing, with no medical/scientific explanation.

I am exactly as skeptical as you would be if someone would try to “sell” you a miracle supporting Islam. Not more, not less.

Try to make is a proper, double blind test. The way to do it is simple. Pick a group of people with the same kind of problem, or disease. Split them into two groups, one test group and one control group. Send the test group to Lourdes, and send the test group to some other place.

After a pre-determined time elapsed, check if there was a significant difference in the healing ratio.

This is the same methodology which is used when a new drug is tested. Nothing special about it.

So it is NOT an evidence for the intercession. So it is NOT an evidence for a miracle. After all JPII was canonized for this intercessory miracle. People, even with the best intentions are prone to commit errors. The best way to protect against them, is to get the help from the professional masters of misdirection - the stage magicians.

Again, try to recruit a bunch of people with well documented problems - before the intercessory prayer starts. And then see what happens.

1 Like

Of course. You – and only you – are in possession of the truth! :rofl:

Only if your “lack of positive outcomes” have a reasonable chance of success. Like I’ve mentioned to you many times: if you’re trying to prove the claim “lions do not exist”, and you only search for lions on the North Pole… you’re not going to prove your claim.

Self-contradict much?

OK – I’ll bite: what’s a “seemingly positive” outcome, in contradistinction to a “positive” one? :popcorn:

I assert that it’s impossible to predict when a miracle will happen. (Thus, it’s impossible to test any validly-constructed thesis regarding the existence of miracles.)

Not that I called it, but…

Go figure. :man_shrugging:

It’s amazing that you’re still not getting the gist of it. Are you claiming that you have a heuristic for predicting when one of these physical miracles might happen? If so, then let’s see it. If not, then please stop conflating the assertion “we can measure physical stuff” with “we know when ‘bona-fide’ miracles are about to happen”. It just makes you look kinda… irrational, ya know?

Of course we don’t. We freely admit that you might be in error, or cheating, or just joking. :wink:

1 Like

Nothing ‘special’, but everything’s wrong about it. Prayer isn’t “medicine”. It isn’t a great cosmic slot machine (put in your “Hail Mary” and hope to hit a big jackpot). As I’ve recommended many times already to you, it would be helpful to you, I suspect, if you read what the Church really teaches about prayer. It’s one of the four main sections of the catechism. Please read it; it might help you to stop making ridiculous claims.

In short: prayer isn’t therapy, so a hypothesis and an experimental procedure designed to treat it as such will fail every time. Not because there aren’t miracles – but because the approach is invalid.

1 Like

But it is possible to predict that a miracle will NOT happen. So here the prediction for you. If you assert that a miracle could happen, THEN it would be your job to predict it. For me it is sufficient to be able to predict that it will NOT happen. Savvy?

Let’s say that your hypothesis is that taking a pebble and let it drop, it will float upwards. After a million tests you find that the hypothesis was not borne out by the experiments - so you drop the hypothesis (along with the pebble) :wink: . But if your hypothesis is that the pebble will drop when released, then a million experiments will be a very strong indication (not a proof!) that your hypothesis was correct. Savvy???

Sorry, it is you, who don’t get it.

There are two different approaches. One is to predict that a miracle will happen. The other one to experience something that contradicts the known principles of the physical reality - with ot without a prediction. The first one would be “superior”, but the second one would also be sufficient. Whether anyone can predict the rearrangement of the stars to display the text in the bible - is not necessary. The mere fact would be a physical miracle.

Of course to predict it would be even more interesting, but not necessary. You have this hang-up on prediction, as if that would be a necessary pre-condition for a miracle. When will you realize this? And I WILL predict that the miracle will NOT happen.

This remark of your proves that you have no idea what the problem is.

If you ask for some miraculous healing, it certainly is. But the principle is still applicable, no matter what. You have a hypothesis, you perform experiments, count the positive outcomes and the negative ones. Then you can perform a chi-square calculation and find out what is the probability that hypothesis is correct.

Let me repeat it: "ANY hypothesis! Not just medication. " Do you finally get it now?

DISCLAIMER: The views and opinions expressed in these forums do not necessarily reflect those of Catholic Answers. For official apologetics resources please visit