Falsifiability is not his idea; it was promoted by Karl Popper. https://en.wikipedia.org/wiki/Falsifiability
Popper made contributions to science in that he was one of the main thought leaders that began the field of philosophy of science. That said, I don't think falsifiability by itself is a very good criterion for science or truth.
I don't think the wikipedia article on this is very good. The encyclopedia of philosophy has a much better overview of his theory and where it stands currently
Science 'works' today by p-hacking and data falsification.
I'm not sure that we should consider current practices an argument against a quality threshold.
But I take this particular context to be about Sagan's comments on distinguishing truth from "baloney" via science by expressing principles that best express the scientific ideal. I don't take that to be "corrected" by appealing to science as practiced, which is where the mixing up of the two comes in.
But I think there's also a separate distinction between good faith and successful enough attempts to do science, and people just gaming the system. The fact that there's plenty of the latter must be acknowledged (in fact, I think the people who discovered this current set of issues and made a big deal of it are from the same group of academics as the ones abusing this loophole, and also, it's likely to be a perennial problem), but the former also exists and is not the same as the abstract ideal you bring up.
I'm not sure I would characterize Sagan's system here as specifically best expressing the scientific ideal. I think it's a great list to think carefully about to help with clear thinking, but I'm not sure applying the label of 'science' to all these points is the right way to think about them, although I'm not sure it isn't either.
Science is a method, not a thing. I think most scientists, including those looking into string theory, would agree that the hypothesis is not science. It's a hypothesis. Maybe not even that, depending on whether or not you think it's falsifiable. But either way, it's an intriguing idea that scientists are looking at. That's a legitimate part of the process as well.
The universe evolves, life just found a way to make it quicker. Then we invented sexual dimorphism to make several selections within a single generation. Our human intelligence allows us to evolve ideas at an even faster rate.
The effects of evolution are in the realms of science, but evolution itself is the superstructure science, and anything else, has "evolved" in. It's time.
Or, using backward reasoning, what would be the simplest possible way to achieve life as complex as a human? Evolution.
But then you start asking questions like where did god come from and why did he do what he did and the simplicity starts to fall apart.
Really, the moment the words "there's an omnipotent being that..." are uttered, simplicity goes out of the window.
Falsifiability just means there's some possible way for it not to be true?
Parts of the theory like Mendelian genetics are testable but on the whole... Evolution happens so slowly that we can't observe it or test it in a lab.
To me it seems like with Popper inquiry into how species came to be can never fit into science. It's a much narrower view than what we commonly understand as science today.
To falsify a theory does not require to reproduce it in a lab. It means that the theory predicts something that you can actually observe, or not observe and thus disprove it.
For instance, we can falsify the theory like this: let's grow bacteria and subject them to some poisonous chemical. The theory predicts that, after many generations, if the colony survive then it should become resistant to that poison.
Here is an example of a theory that is not falsifiable: after they die, people's souls go to a place that is impossible to observe when you are alive.
Falsifiability is about "impossible to observe", not about repeatability.
Evolution is frequently observed in the lab, particularly in organisms the reproduce quickly and prolifically as in most microorganisms. You might want to google "antibiotic resistance", which is literal evolution creating a public health hazard.
Evolution has withstood well over a century of experiments. It's the inevitable consequence of the facts of inheritable mutations and natural selection. Biology doesn't even make sense without it.
Sean Carroll talks pretty positively about string theory. I think he paints the picture that although the popular view is it's not falsifiable (or not yet), therefore it's somewhere between very suspicious and junk, but actual theoretical physicists are much more positive about it.
I don't think Popper was going for that soft falsifiability - but if you modify his theory to do that, say it has to make some predictions, and only require that it should be falsifiable on the basis of it's predictions, you let in a lot of stuff in that obvious isn't science.
To take the obvious example of using exactly what Popper was trying to oppose. the current Chinese communist party's claim that capitalism will eventually transition into socialism once a certain level of development is achieved, it is a prediction, it will be falsifiable later. Clearly it is still not science.
But even if we give Popper the falsifiability angle and imagine there is some workable version of falsifiability, I still don't thik his theory works, it's just not a good reflection of day to day science and scientists.
I think this is the point on this issue, right? It can't count as falsifiable later, or still not science, unless they describe what they mean by "socialism" specifically enough in advance - which I think is a pretty nebulous constraint? Not sure about it. Definitely, there's a lot of (reasonable IMO) theoretical controversy about what 'welfare capitalism' has to do with proper socialist ideas, even though it's usually given the label 'socialist'.
I've also been wondering things like what working scientists do, and what this thing is that we call science generally - non research related stuff like teaching, or using science to do better engineering, and what the connection is between the two.
Is there still a place for any variation of falsifiability?
Bonus cheeky request: do you have any recommendations on modern philosophy of science?
I accept Quine who I admit isn't much better, he thinks it's all about creating a coherent world view. I think he's onto something but he's missing truth which I think is a problem - we want to think science gives us truths about the world, or at least we want a way to get to truth.
There's another view that says science starts with a set of untested assumptions which I haven't gotten around to reading much about
I listened to a few interviews with Liam Kofi Bright, and his ideas about what truth is are pretty interesting. The perspective of 'giving us truths' or 'getting to the truth', is unsatisfying to me.
I think there has to be a core of some kind of 'predict what will happen when we do something, then see how close we got, tweak it in response to these observations, then repeat'.