What is Evidence?

Is there evidence of life after death? Before we answer that, let's get this straight: What is that - evidence?

The answer depends on what we're talking about: mathematics? Physics? A court case?

Mathematics...
Absolutely compelling evidence – proof –, against which no objection is possible, only exists in abstract disciplines such as mathematics and logic. Here everything takes place within a purely formal system according to clearly defined rules. In all other sciences, whatever we may call proof or evidence must be measured against the reality that surrounds us.

 ... Physics ...
Physics and chemistry come close to the absolute certainty of mathematics because they can be mathematically modeled and experimentally repeated as often as desired. Newton's theory of gravitation, for example, can be expressed in mathematical formulas that allow very precise predictions. Their correctness can be checked experimentally at any time. Nevertheless, Newton's theory is today only considered an approximation of physical reality, very practicable indeed, however, Einstein's theory of relativity has proven to be more precise and appropriate. So, even a mathematically modeled theory that has been tested countless times can one day be replaced by a better theory.

 ... Climate Research ...
Experimental verifiability is a strong criterion. But we shouldn't apply this standard to all scientific theories: the Big Bang, for example, is a unique event in the past. That it happened can be inferred from observable phenomena, but the Big Bang cannot be repeated in experiments. We should also not demand experimental verifiability from the climate sciences, because the catastrophe they warn about will only unfold its full force in the future. Whether the worst can still be averted depends on conditions that climate research cannot fully grasp and certainly cannot control. Only this much is certain: We must act before the climate collapses – in other words: before we have the ultimate proof that the disaster warning was correct.

... Biology ...
The criterion of mathematical modeling is also not applicable to all scientific theories. In biology, for example, experimental verifiability is possible: countless laboratory rats can be tortured again and again with the same experimental setup. But the results cannot be poured into mathematical formulas.

We have to make further cuts in the case of scientific theories, which can neither be mathematically modeled nor experimentally tested. This applies, for example, to the theory of evolution or to paleontology, i.e. the science of historical creatures that are only available as fossils. But even such theories can be very valid if they are confirmed by large numbers of high-quality finds.

... the Multiverse Theory ...
And then there are scientific theories that can neither be tested in reality nor mathematically modeled nor experimentally repeated. Such theories have no probative value, they are pure speculation. An example is the multiverse theory, according to which there are other universes outside of our universe. Whether this is true cannot be determined.

... History...
Let's leave the sphere of the natural sciences and turn to the historical sciences. They are in a less comfortable situation: their subject is historical events. These can only sometimes be confirmed by archaeological finds, such as the sudden end of Pompeii. Often historians have to rely on a few written sources, sometimes written decades after the event reported. Can we trust such sources? Whatever the answer may be, historians are treading on comparatively thin ice. We have to accept that, if we want to learn something about important events from antiquity and the Middle Ages.

… in Court ...
Also, many court judgments are not based on physical evidence, but on the testimony of witnesses. If credible witnesses make statements under oath that do not contradict each other or the real world: then these statements are accepted as evidence. In chemistry, this would be unthinkable. In the legal system, it's enough to put people behind bars for years. 

... afterlife research.
And what about possible evidence of life after death: what standards should apply here?

Many want to set the standard so high that it cannot be reached by any kind of research, because: "extraordinary claims require extraordinary evidence". After all - so they reason - the assumption of an afterlife would call into question everything that the natural sciences have so far discovered.

I think that's wrong. If there were to be a dimension that goes beyond what can be scientifically ascertained, then nothing would change in natural science at all. The question of the hereafter should be examined in the same way as other questions: if it turns out that experiments are possible, then let's do them. If, on the other hand, experiments prove impossible, let us not demand them. If we would have no other evidence with this subject than testimonies, then we would have to content ourselves with examining them.

Would you allow this testimony to the afterlife trial?
In the 1970s, in the emergency room of a psychiatric institution, a young doctor was talking to a  woman who had tried to commit suicide and just come out of her coma. When he had examined her the day before, she had not yet been responsive. At that time, he had left her to go into another room and have a conversation with another patient.

When a day later he examined the suicidal woman again, she was just waking up and able to respond to him: "I know you," she said. - "It's possible," he replied, "I examined you yesterday." - "No, I don't mean that," she replied.

And then she described to him in detail what had happened to him after he had gone to the other room the day before: with whom he had spoken and about what, where he and his interlocutor had been sitting, what he had been wearing and how both had moved. That is, very specific details that she couldn't possibly know, and yet she knew.

The doctor who reported this personal experience is Bruce Greyson. Previously a convinced atheist, this experience made him a co-founder of the International Association of Near-death Studies (IANDS) and one of the most important near-death researchers. I cannot provide evidence that what Bruce Greyson reported about this experience is true. But I got an impression of his personality and let his report work on me. Since then I can't help but believe him.

So I have no evidence with which to refute a skeptical commission, but one that does convince me. It is not surprising that such evidence convinces some, others not: witness testimonies are not as compelling as mathematical proofs. I suggest we allow them anyway. After all, this isn't about math.

 This post is based on a chapter from „Dieu - La science Les preuves: L'aube d'une révolution“ by Michel-Yves Bolloré and Olivier Bonnassies (2021).