A listener of my podcast, the Skeptics Guide to the Universe, sent in the following question:

“Okay, so chiropractic, acupuncture and reiki don’t work because the energy flows they are based on don’t exist. So here’s my question…how do we know they don’t exist? How do you test something like that?”
– Gregory Lynn

Mr. Lynn’s question is a reasonable one, and one I get quite frequently, but it contains a serious and common misconception – actually two. The first is that the burden of proof is on those who claim that a life force, or spiritual energy, does not exist. The second is that scientific methods can be used to test for the non-existence of something.

Generally speaking the burden of proof rests with those who claim that a phenomenon exists – not those who are appropriately skeptical of the claim. There is also a superceding criterion for determining where the burden of proof lies, however, and that relates to what has already been established and accepted as scientific fact. A claim’s burden of proof increases in proportion to its contradiction of established fact. You can also apply Occam’s Razor, in that if a claim requires one or more new assumptions about the nature of reality (even if it does not contradict what is already established) that will likewise increase the burden of proof.

But all that aside, how would a scientist answer the question as to whether or not a phenomenon exists – such as the life energy central to many so called “alternative” healing modalities like those mentioned by Mr. Lynn? As a point of logic, it is impossible to prove a negative – that something does not exist. But scientific inquiry can set limits on existence.

For example, if a person were subjected to every known scientific instrument used to measure different energies, and no “life energy” were detected, we could say that no energy exists that can be measured by the instruments used and at a strength that is within the sensitivity of those instruments. But this does not rule out a force that either does not interact with the instruments used or is too weak to be detected by them.

The greater the thoroughness and sensitivity for which a phenomenon has been searched with negative results, the higher the confidence in its non-existence (but such confidence can never reach 100%).

But in most cases it is more meaningful to ask the question – how do we know a phenomenon exists, or why would we even hypothesize its existence. The notion of a life force is a pre-scientific one, invented by peoples who had no knowledge of how living organisms actually worked. Modern biology, by contrast, is a rather mature science. We have a very good idea, down to minute detail in many cases, how life functions. Further, there are no big mysteries remaining about basic life functions. So there are no life phenomena that defy explanation by conventional means – anything that would lead us to consider that an undetected force is at work.

Therefore, from a scientific point of view I would say that the notion of life energy is simply unnecessary. There is no reason to hypothesize its existence. Proponents of certain pre-scientific healing modalities claim clinical effects that are based upon life energy – but no such modality has been demonstrated scientifically to be effective. Until there is compelling and reliable evidence of such effectiveness, life energy remains condemned to the outermost circle of scientific rejection – superfluousness.

Some life energy practitioners, such as users of Therapeutic Touch (TT) claim that they can sense a “human energy field.” Therefore they are saying that human sensation is an instrument that can detect life energy. But when this claim was famously subjected to a very simple test (by an 11 year old girl, nonetheless), practitioners failed to demonstrate that they could detect such a force.

When confronted with the complete lack of evidence for the existence of a life force, proponents will often use the “invisible dragon” defense (ala the excellent example given by Carl Sagan in Demon Haunted World). Basically they say that we cannot see life energy because it is invisible to all means of detection. It is reasonable to consider whether or not an instrument should be able to detect a phenomenon you are using it to look for – but when every attempt to detect life energy fails and is met with the excuse that “it doesn’t work that way” or “it cannot be detected by that method,” we get into what is called special pleading.

So even though we cannot prove the non-existence of life energy, there is no reason to think that it exists, and all attempts to demonstrate its existence have failed. Therefore it is both unnecessary and improbable. And that is enough.