Affirming The Consequent In The Search For Ghosts

Suppose – just for argument’s sake – that ghosts are real. And suppose, again, that when a ghost is in your vicinity, it affects the magnetic field around it.

Now imagine you are on a ghost hunt, run by one of the hundreds of ghost hunt companies that exist – those commercial enterprises that claim to take you through a haunted location to find evidence of the paranormal. An overnight vigil, perhaps. You pay money to go on a ghost hunt, and you are offered the use of scientific instruments in your pursuit of the supernatural.

Scientific, remember.

One of the scientific instruments you might use is an EMF (Electro Magnetic Field) detector. They seem to be very popular within the ghost hunting fraternity. So, assuming that ghosts are real, and that they affect the magnetic field in their vicinity, a basic logical proposition can be formulated:

If there is a ghost present, then there will be a variation in the local magnetic field.

So, you set off in pursuit of ghosts, and after a short while, the needle on your device’s dial flickers and moves to a point showing a definite magnetic anomaly. Bingo! You’ve found a ghost. Or have you?

Numerous paranormal “experts” will quite happily tell you that there is a “theory” that the presence of ghosts will give readings on EMF detectors, and so if you get such a reading then it is indicative of a ghostly presence. It’s logical, isn’t it?

In fact, no, it is definitely illogical – a non sequitur, as it happens. I’ve assumed for the above scenario that ghosts are real. If they were, and they did cause magnetic anomalies, then it would be true that a ghost in the area would cause a deflection of the needle (or flashing lights) of your EMF device. But the fact that a magnetic field can change (or just be there) does not indicate, logically, that a ghost is present (even assuming that ghosts exist).

This logical fallacy occurs in formal logic when it is assumed that if particular premises imply a particular conclusion, then the conclusion also implies the premises.

The logical form alluded to above is called Modus Ponens. It goes like this:

If P, then Q.

P, therefore Q.

For “P” read, “A ghost is present.” For “Q” read, “There is a magnetic anomaly.”

In formal logic, the above is called a valid argument because the conclusion necessarily follows from the premises. (Strangely, however, neither the premises nor the conclusion of a valid argument have to actually be true in the real world; the important thing is that the conclusion follows from the premises. I’ll come back to that later.)

So if a ghost causes a magnetic reading, why can’t you take it that when you get such a reading that a ghost is around? The simple answer is that there are lots of things that can cause magnetic fluctuations. In any modern building (and old ones), you are literally surrounded by magnetic fields. Electrical wiring is all around you, so it just takes someone to operate an electrical light or appliance somewhere nearby to cause a fluctuation that can be measured. Metal objects nearby will also affect a magnetic field. Anything with an electric motor, especially, will do the same. Even if a ghost could affect a local magnetic field, there are many other possible causes as well.

In short, a magnetic variation can have numerous different causes, and there is no way to tell what, in particular, is causing the altered reading.

The fallacy is called “affirming the consequent.” It’s quite common, in fact. On a mundane level, try this:

If it is raining, then the ground is wet.

It is raining, therefore the ground is wet.

Modus Ponens, and valid reasoning to boot. But if someone came indoors and told you that the ground is wet, should you conclude that it is raining? The simple answer is no, you shouldn’t: you can easily think of several reasons why the ground might be wet without the need for rain. A burst water main, perhaps, or your neighbours are watering their gardens, and anything else you can think of.

If the ground is wet, it might, indeed, be raining, but it might be something else. The fact that P implies Q does not mean that Q therefore implies P. (There is an exception to this rule when a logical argument is also a biconditional – another post for another day.)

A similar thing happens in other aspects of paranormal research. ESP researchers spent decades trying to prove the existence of telepathy – quite often with the use of Zener cards. Essentially, a potential psychic is presented with series of cards, each of which have one of five possible symbols printed on it. Over a series of tests, the psychic’s task is to identify by psychic means the symbols as they are drawn randomly. Pure guesswork should give results that align with chance expectation; psychic abilities should enable the psychic to identify significantly more than would be expected by pure guessing.  The reasoning among psi researchers has tended to go (If P then Q):

If ESP is at work, then the (statistical) results will deviate from chance.

The results deviate from chance.

Therefore, ESP has been confirmed.

Unfortunately for the believers, there are many other reasons why the results of psi tests might deviate from chance – none of which has anything to do with the paranormal, including poorly designed experiments – anything from poor experimental controls to the great bane of paranormal research, outright fraud. Like the examples above, the assumption is that if the premises imply the conclusion, then the conclusion must imply the premises. But it just ain’t so.

The first sentence of this post was, “Suppose – just for argument’s sake – that ghosts are real.” And that is where the problems start. So-called ghost hunters assume at the outset that ghosts are real entities – immaterial, maybe, but the assumption is that they are real, nevertheless. But no one has actually demonstrated that ghosts are anything other than wishful thinking on the part of the believers. There is no confirmable, testable evidence that ghosts exist (whatever your definition of a ghost might happen to be). How do the experts know that ghosts (if they exist) affect magnetic fields anyway? The short answer is that they don’t.

EMF detectors are useful for detecting electromagnetic fields, and there is no reasonable doubt whatsoever that the electromagnetic spectrum is real. Electric motors, for instance, could not exist otherwise. Electromagnetism from the far ultraviolet, through visible light to the far infrared is a reality and all of it can be demonstrated scientifically.

Ghosts, on the other hand, are a made-up idea to explain phenomena that sometimes do not have an obvious or demonstrable explanation. If you find an electromagnet field with your EMF detector while you are looking for ghosts, so what? You will have found an electromagnetic field, alright, but why should anyone think that a ghost is causing it?

As I said earlier, neither the premises nor the conclusion of a valid argument need to be true in the real world. Think of the characters in a novel, for instance. For a story in a novel to work, all of the elements have to have a clear logical relationship to each other, even though the characters, places and events don’t exist in the real world.

If Merlin is a wizard, then he can perform magic.

Merlin is a wizard, therefore he has magic powers.

That’s fine in the context of the story of King Arthur even though the characters in the story are nothing more than myth, at best. But in the same story, a character that has magic powers is not necessarily Merlin. The fact that Morgana has magic powers does not make her Merlin.

The essential point to keep in mind in all of this is the form of logic that appears in an if/then scenario. It is “true” that if Merlin is a wizard then he has magic powers – at least in the sense that the conclusion follows from the premises – even though Merlin is not a real person, and magic is nothing more than fantasy.

It cannot be said too many times that it is the relationship between premises and conclusion that is important. For a conclusion to be true in the sense of being real, then the premises also have to be true. Before it can be claimed that ghosts affect magnetic fields it is first necessary to demonstrate that ghosts are real, and then show how it is that ghosts affect an electromagnetic field. Until someone can do that, you can be sure that EMF detectors are a complete and utter waste of time and money for anything other than the job they were designed for.

I assume that the people who run these ghost hunting expeditions do believe that ghosts are real and that they can be detected by electronic gadgetry with dials and blinky lights and so on. I also assume that they have no understanding of basic logic.

The bottom line.

Modus Ponens is part of formal logic, and is also known as deductive logic.

The conclusion must follow from the premises for the argument to be called valid.

The premises of such an argument imply the conclusion, but the conclusion of that argument does not imply the premises.

If you do happen to go on a ghost hunt and you use an EMF detector, just keep in mind the fact that you might be able to detect magnetic fluctuations, but those fluctuations tell you absolutely nothing about the existence or presence of ghosts or anything else allegedly paranormal – even if ghosts were real (and I’m pretty sure they aren’t).

Using EMF detectors to find ghosts is nothing more than pseudoscience, but the assumption that you can detect ghosts with such a device is just bad thinking. If your ghost hunting host tells you that an EMF detector is useful in any way for detecting ghosts, ask him if he knows what the logical fallacy affirming the consequent means. At least you know what it means – now.

Just for fun:

Here is a logic puzzle for you to try if you want to. It is a basic puzzle that will probably be familiar to people who have studied logic, but anyone can have a go at it. I’ll wait to see if anyone wants to try it and put their answer in the comments (with the reasons for their conclusion). In a couple of days, I will post the actual answer in the comments.

Here we go:

In the next street to where you live, all of the houses on one side of the street are bungalows. On the other side of that street, all of the houses are detached houses.

Here’s the funny thing: the people who live in the bungalows always tell lies.

The people who live in the detached houses, however, tell only the truth.

One day, you meet three men who live in that street. Let’s call them Tom, Dick and Harry. After the initial meeting and introductions, you ask Tom, “Do you live in a bungalow or a detached house?”

But Tom mumbles something you can’t hear. So you ask Dick , “What did Tom say?”

Dick replies, “He said he lives in a bungalow.”

Harry immediately turns to you and says, “Don’t believe Dick, he’s a liar.”

The question is: does Harry live in a bungalow or a detached house?