The demarcation problem is the problem of characterizing the difference between science and non-science, of finding criteria that can say whether a given idea or theory or practice is scientific or not.

It is a problem because no accepted solution has been found: everytime someone comes up with criteria, either these criteria classify as scientific some ideas/theories/practices that are widely considered as unscientific, or they classify as unscientific some that are widely considered as scientific.

The consequence is that an idea/theory/practice is not considered unscientific because there are objective criteria that show that it is unscientific, but because some authority or majority have decided to label it as such, based on their own subjective desires. And then it becomes that appending the label "unscientific" to an idea/theory/practice is a way to discredit it arbitrarily, not by comparing it to objective criteria but to one's personal motivations.

This is an aspect of science that has far-reaching implications and yet I don't ever see it mentioned in discussions that involve science on this forum, so I feel it is important to point it out.


Some people use the demarcation criterion that a scientific theory is a theory that can be verified through repeated observation by many different people, which they use to label as "unscientific" the theory that God exists, which in fact is already problematic because many people have claimed to have felt God repeatedly. But the bigger problem is that this criterion classifies as unscientific pretty much all theories that are considered scientific, for the simple reason that even if a theory has agreed with observations N times, there is no way to prove that it will agree the next time, there is no way to verify it.

Based on this realization, some people have come up with the criterion that a scientific theory is a theory that can be falsified, that is there is a way to compare the theory with observations and so to check whether the theory agrees with observations or not. If an observation disagrees with the theory, then the theory is falsified. If no observation can disagree with the theory, then the theory is not scientific. They then use this criterion to label as "unscientific" the theory that God exists (as one example among many others), because it seems that no observation can disagree with that theory. But the problem, again, is that pretty much all theories that are considered scientific cannot be falsified, because if there is an observation that disagrees with the theory, there is a way to save the theory by assuming that there was a phenomenon that wasn't accounted for that is responsible for the disagreement (such as dark matter, dark energy, an unseen planet, a new particle, something invisible, ...), or by assuming that the measuring instruments that were used didn't work properly.


So as it turns out, a theory is not verified or falsified based on objective criteria, it is said to be verified or falsified when an authority or majority agree to call it verified or falsified. In other words, it is not objective criteria that decide whether a theory is accepted or discarded, it is the personal motivations of some authority or some majority.

The implication is that theories are abandoned, discarded, rejected, not because there was no way to make them work, not because it couldn't have been fruitful to consider them seriously or to explore them further, but because some authority or majority have decided to abandon them, discard them, reject them. And then it appears clearly that science is not the objective questioning of nature devoid of conventions and politics that most imagine it to be, it is a social enterprise. The observations that are made and the theories that are accepted are framed in a way that they suit the motivations and beliefs of some influential individuals or groups.

And this is even more exacerbated when we consider that the theories and lines of research that are explored and worked on are those for which scientists receive funding, and the research that gets funded is decided by the individuals or groups who provide the funding and the influential individuals or groups who advise them.

And then there is no basis to dismiss a theory because it has been labeled as unscientific, nor because it was abandoned or rejected by the mainstream, nor because it isn't explored by the mainstream, that theory could potentially be fruitful and lead to great discoveries. And an objective questioning of nature would allow these theories to flourish, rather than ridiculing them and their proponents and those who want to work on them, which is more reminiscent of the practices of a dogmatic and oppressive community than that of a community driven by the sole desire to understand.