Sabine is on the case: What’s the difference between valid speculation and bad science?

Sabine Hossenfelder, Can Physics Be Too Speculative? Backreaction, July 24, 2021.

She acknowledges that speculation is critical to intellectual progress, but...

The question how much speculation is healthy differs from the question where to draw the line between science and pseudoscience. That’s because physicists usually justify their speculations as work in progress, so they don’t have to live up to the standard we expect for fully-fledged scientific theories. It’s then not as easy as pointing out that string theory is for all practical purposes untestable, because its supporters will argue that maybe one day they’ll figure out how to test it. The same argument can be made about the hypothetical particles that make up dark matter or those fifth forces. Maybe one day they’ll find a way to test them.

The question we are facing, thus, is similar to the one that the philosopher Imre Lakatos posed: Which research programs make progress, and which have become degenerative? When speculation stimulates progress it benefits science, but when speculation leads to no insights for the description of nature, it eats up time and resources, and gets in the way of progress. Which research program is on which side must be assessed on a case-by-case basis.

She goes on to consider several examples:

• Dark matter
• Early universe and fifth forces
• String theory
• Multiverse theory
• Is Oumuamua alien technology?

I don’t think there’s a clear line between valid speculation and intellectual nonsense. I doubt that Hossenfelder does either; she certainly doesn’t make any such claim. The problem we have to place we can ‘stand’ and observe science from the outside and thereby observe what lines of investigation where heading towards truth and which ones were just lost in the wilderness. If such a point of view were available to us, we’d just go to it and then zip right over to the truth, skipping the painstaking process of scientific observation entirely. Thus the problem of distinguishing valid speculation from high-class nonsense is something the community must solve however it can.

I’ve become interested in a related problem: When does a fruitless line of investigation resort to signaling behavior to close itself off from the world? Signaling is simply the superset of what has become called virtue signaling in a variety of current debates surrounding issues of social justice, but also conspiracy theories. To emit a signal, in this sense, you assert a belief that many consider to be outrageous in order to affirm your solidarity with some in-group. You affirm your loyalty to Donald Trump by asserting (among many other things) that, yes, his was the largest inauguration ever. You affirm your loyalty to QAnon by asserting your belief in a worldwide ring of Satan-worshipping pedophiles. And so forth. Are any lines of degenerate science in such a zone?