the demarcation problem exists because of astrology being a pseudo science!

Astrology isn't a pseudoscience because of the subject matter, but because of how the practitioners operate in terms of sharing knowledge. If they operated scientifically, astrology would be a science, and the scientific answer would be, the stars do not affect us in the way astrologers predict. But they don't operate according to scientific principles, so they reject the scientific answer and keep on making up nonsense.

@TKoL I am not asking why astrology is considered pseudoscience at all. My question is that if I state so, then I am more or less implicitly drawing a line between science and pseudoscience, with perhaps unwanted consequences...

The "demarcation problem" means it can be difficult to classify items which do not clearly fall on either side of a demarcation line, or where the choice of demarcation line is controversial in some way. Neither of those problems actually exists in the demarcation between astrology and science.

@kaya3 Yes, you can just say that it is obviously so. My point is that you have to give reasons for that (there are plenty), but then you could run into trouble that certain criteria also apply to other fields/subjects, which one would like to call science (or does so). That's my point/question...

Sure, each demarcation line you might draw between astrology and science will have its debatable edge cases, which means that there may be a demarcation problem for those edge cases. It doesn't mean the same problem applies for astrology, because astrology isn't one of those debatable edge cases.

Likewise, there might be debate over which exact line to draw between astrology and science, because some lines might have things on one side which people think should be on the other side. But that isn't a problem for science vs. astrology either, because all the lines being drawn put astrology on one side and science on the other; the disagreement over which line is correct, doesn't impact the conclusion for astrology, even if it might impact the conclusion for other cases.

It's a bit like asking how we can consider Newcastle to be in the North of England, when there is no universally agreed line separating the North from the Midlands. That's not a problem when every line people draw still has Newcastle unambiguously in the North. The debate over which line is correct and which cities are on which sides of that line, does not need to be resolved before we can affirm that Newcastle is in the North.

The problem is not just the demarcation between science and pseudosciences, but also the definition of astrology. There isn't a single theory that uniquely identifies astrology, it's a bunch of practices that are loosely connected. Some of which don't even pretend to be scientific.

@kaya3 "even if it might impact the conclusion for other cases" that is of course what my question is about... Again: If you say we are not "in danger" for all other "reasonable" fields, then this gives you sufficient conditions for something to be pseudo science (whatever "safe" line you draw to identify astrology as pseudoscience). If you'd like, consider to summarize all your comments in an answer, would be helpful. Thanks in any case.

@JasonFunderberker I don't think you understand what I was getting at. You're talking about the demarcation problem like the subject matter of astrology is inherently unscientific. I'm saying it's not. There is no demarcation problem here. The subject matter of astrology is explicitly scientifically investigable. It's astrologers who are unscientific, not the subject of astrology itself.

The answer to "why can I call astrology a pseudoscience if the border between science and pseudoscience is not precisely-defined?" will be the same as to "why can I call a quad-bike a quad-bike and a car a car, if the border between different types of four-wheeled vehicles is not precisely-defined?" and likewise the border between a chair and an armchair, and pretty much all pairs of words in the dictionary. And yet we use words all the time!! Only in technical domains, and for the purpose of laws and regulations, do we actually rely on precise definitions. Everything else is fuzzy.

@TKoL I do agree with the very most you are saying. I don't see any statement of mine which would suggest otherwise. With "subject" I mean not only astrology or physics or whatever itself, but the active process of doing/practicing it, (very) roughly speaking. Which, I think, is the usual understanding...

@Stef Thanks for your comment. So you do think the demarcation problem is "useless" to some extent? If so, fine, you can have that opinion, but it is not what I am asking about. Sorry if I misunderstood you.

@JasonFunderberker I think it's important to understand the way we use words in mathematics, and the way we use them in law-making, and the way we use them in everyday language. In everyday language, drawing hard lines is pretty much impossible for almost everything. And yet we can communicate. Drawing arbitrary lines would be possible for some things, but still hard or impossible for others, and not particularly useful anyway.

But if you're asking about the demarcation problem for pseudoscience in particular (as opposed to categories in general) and for astrology in particular, then I think it's important to remember the context. The real world can't be abstracted from the discussion. If you and I truly didn't know whether the position of planets at birth had an impact on an individual's fate, and if we truly tried to answer that question objectively, then our exploration of astrology would be a science, although the boring conclusion would just be "nope, no impact".

But the history and practice of astrology in the real world is clearly unscientific. It's a scam and nothing more. That's why we call it a "pseudoscience" and frankly even that word is a euphemism.

Because in some case there are difficulties it means that we can never do anything. QED

Science involves many principles, and pseudoscience could not follow scientific principles in any number of aspects to any degree. So the demarcation wouldn't be a line but rather a multi-dimensional frontier. I think it's more important to call out the specific ways in which any particular discipline fails to stay rigorous to the scientific method than it is to black-and-white label it as either "science" or "pseudoscience". Much like how you can't simply categorize all people as either good drivers or bad drivers.