Objectivity, Quantum Mechanics, and Bad Logic

Recently I read a paper where some physicists were testing interesting repercussions of quantum mechanics. Their work made eye-grabbing headlines such as Objective Reality Doesn't Exist, Quantum Experiment Shows. That's quite a bold claim considering the long history in philosophy specifically on the question of subjectivity vs. objectivity. Seeing them confidently dismiss objectivity I knew I had to see why they were so confident of their conclusions. Unfortunately the physicists walked naively into a well known philosophical topic, like a knitting club into a Black Sabbath concert.

So let us take a look at what lead them to their conclusion that objective reality does not exist. This may get a little technical, but stay with me.

They designed an experiment that could specifically test objectivity (O), locality (L), and free will (F). They point out that previous proofs have established L and F, and LF together, so if they test OLF then the experiment can establish or undermine the idea of objectivity (O).

In their paper the physicists defined objectivity as the existence of "observer-independent facts, stating that a record or piece of information obtained from a measurement should be a fact of the world that all observers can agree on—and that such facts take definite values even if not all are “co-measured”." Thus they are testing whether a measurement creates an objective fact for everyone or if the result depends on the observer.

Locality means each measurement must happen in such a way that the result only depends on local factors and not on any other measurement in the experiment. (In technical language the future light cone of one measurement cannot be in the past light cone of another measurement.)

The last assumption is free will. The people in the experiment must be free to make their choice and not have their choice predetermined in any way, either by the first measurement or any outside factors.

In the experiment they have someone (who they call Alice) who is given a choice. In a lab Alice has a friend making measurements of individual photons. The friend can turn on a detector, thus choosing to measure any photons that come through, or turn it off, thus choosing not to make any measurements.

Alice can check what her friend measured, but cannot know before hand if her friend even had photons to measure. So Alice might check on her friend and find they didn't make any measurements because no photons passed through the lab.

Alternatively Alice can check to see if a photon went through the lab and that her friend could have possibly measured it. But Alice cannot check if her friend actually measured it and check if a photon went through the lab (in technical language Alice can measure whether her friend is entangled with a photon or not).

So there are four possibilities. The friend can choose to measure and Alice looks and confirms that her friend made a measurement. The friend can choose not to measure and Alice looks and confirms that no measurement was made. The friend can choose to measure and Alice doesn't look but establishes that her friend is entangled with a photon that could have possibly been measured but doesn't know if her friend measured it. Or the friend chooses not to measure and Alice doesn't look but checks if her friend is entangled with a photon.

In the actual experiment the physicists didn't have someone checking in on their friend. Instead "Alice" was a series of polarization filters and a detector, and the friend was a separate set of filters and a detector.

To make sure they were measuring what they thought they were measuring, the physicists set up their experiment such that there were two sets of detectors, "Alice" and "Bob", each with their own "friend". The photons measured by the friends were entangled which means what one measures will be the compliment of the other. This symmetry allows for easier checking for statistically significant results.

What the physicists found after running their experiment for a few months is that collectively their assumptions were being violated. That is, OLF all together were not consistent with what was being measured. Because both L and F, and LF had been proven through other proofs that meant that O was the weak link.

If OLF all together was true then regardless of whether Alice or Bob checked if their friends made a measurement, or checked if they could have made a measurement, then there should have been confirmation that a measurement was made either way. If Alice and Bob never checked directly on their friends but only measured whether they had an opportunity to make a measurement then they could know just from that whether their friends made a measurement.

But their results showed that neither Alice nor Bob could tell if their friend had made a measurement without actually looking at their friend. They could not infer from the mere possibility of a measurement that a measurement had been made.

This sets up a paradox. The friends can make a measurement and know definitively what state the photon is in, but for Alice and Bob it is as if a measurement had never been made. That is, there is no way for Alice a Bob to know that a measurement had been made without actually measuring their friends.

The "facts" created by their friends (i.e. what they measured) cannot transfer to any other observer without a real transfer of data. If a measurement is made, that measurement does not somehow change the fabric of reality such that we can know that something was measured, even if we don't know what the result was. That information only stays with the first observer and does not transfer in any way to any other observer without the second observer observing the first. It is like there is no master list of all interactions and measurements in the universe that someone could hypothetically look at.

But the major assumption is that once something has been measured, that fact is established and everyone in the universe should, in principle, be able to agree with it. But Alice and Bob cannot establish if a measurement even took place, thus for them that fact does not exist. The interpretation given by the physicists is that two realities exist concurrently. One where a measurement was made, and one where it was not made. This, they conclude, shows that what is "reality" depends on what measurements were made by a subject. Hence everything is subjective and there is no objective reality.

Now the physicists do not make their boldest claims in their paper. They keep it strictly technical and straight forward. I can find nothing to disagree with in their paper. I may not know the technicalities of their set up, but their experiment is not something so unknown that it makes their work suspicious. It is an experiment that would probably be talked about in an undergrad physics class. So their set up is standard and well known. Their methods are standard and well known.

I find nothing wrong with their conclusions in their paper. But like I mentioned at the start, they walked naively into a well known philosophical topic, like a knitting club into a Black Sabbath concert.

In their writings outside their paper they make conclusions that are not logically backed up by their research, nor even backed up by logic at all. Their experiment does show something interesting that there cannot be a "master list" of the states of all particles in the universe. That is, when an observer makes a measurement, that does not change the universe in such a way that anyone else can know that a measurement was made, let along know what the value was.

This shows that all observers are independent subjects. Each of our observations are our own. But this does NOT disprove objective reality.

In setting up the experiment, even just as a thought experiment the physicists had to assume "objective reality". They first had to have "observers" that could be established as observers. They had to have photons and everyone agree, objectively, as to what a photon was, and how to measure it. All of these are objective and are necessary for us to even have the concept of subjective.

David Hackett Fisher, a famous historian, wrote an entire book berating historians for their use of egregious logical fallacies. Even though his book was directed at those of his own profession, its concepts apply to all areas of academic study. It should perhaps be required reading for anyone getting a PhD. In his book he takes a moment to comment on "subjectivity" vs. "objectivity".

"'Subjective'" is a correlative term which cannot be meaningful unless its opposite is also meaningful. To say that all knowledge is subjective is like saying that all things are short. Nothing can be short, unless something is tall. So, also, no knowledge can be subjective unless some knowledge is objective." -- Historians Fallacies by David Hackett Fischer, Footnote 4, page 42-43.

Essentially these physicists, though very gifted, stepped out of their field of study and made a freshman level mistake of logic. In their hyperbole they jumped to an illogical conclusion. As one of my philosophy professors might say, "They abused the fundamental definitions of the words such that the words had no meaning." They showed that subjective knowledge is a thing and then extended that knowledge to encompass all knowledge. They fell victim to my favorite logical fallacy.

Without thinking about it they set up an objective experiment to show that objective reality does not exist.

Normally this is the point where someone would say, "Don't step out of your own field!" but I think that is also a fallacy. Instead I say, "Before jumping to conclusions try to think critically about your conclusions to see if they make sense. If you think you have come to some major conclusion that entirely overthrows everything we know, 99.998% of the time you messed up somewhere."