The phenomena discussed in that comic were chosen for inclusion specifically because they actually would lend themselves quite easily and obviously to commercial exploitation if they really existed as popularly conceived. If you stipulate that all of those alleged psychic phenomena are inherently not exploitable in those ways or any other significantly profitable way, you're basically redefining those terms contrary to their popular meanings and just moving the goalposts.
The same could be said of antibiotics. However, before Ehrlich & Pasteur, there were no large scale use or even specific awareness of the concept (i.e. some cultures had folk medicinal remedies that involved antibiotics but the mechanism and specific compounds were not understood).
So until the 1880s, there was no commercial exploitation of these compounds, yet they nevertheless existed either in actuality or potential. Once there was an understanding of the principles and the development of some related chemical and biochemical processing, this exploded and had a dramatic impact on human life.
If someone postulated in, say, 1785, the idea that perhaps there were specific compounds that could be used to cure infection, and these could be produced en masse, would it not be analogous to respond that since nobody is commercially exploiting (at the time), they clearly do not exist?
> If someone postulated in, say, 1785, the idea that perhaps there were specific compounds that could be used to cure infection, and these could be produced en masse, would it not be analogous to respond that since nobody is commercially exploiting (at the time), they clearly do not exist?
None of the ideas included in the xkcd comic are particularly new or obscure. Despite being pigeonholed as a certain kind of bullshit, they are still ideas that a lot of people have heard about and been hearing about for a very long time—more than enough time for someone to get around to commercially exploiting if that were in fact practical. Ghostbusters came out 37 years ago, and the stuff it made fun of was familiar enough to its audience.
However, in 1785 the principles of chemical engineering were largely unknown, precluding the development of a modern-style pharmaceutical industry. It did not, however, prevent widespread use of antibiotic treatments that we now understand the mechanism for and can refine or synthesize into more effective forms.
