Harmless means absence of harm. That we don't know of any harms does indeed not mean there aren't any harms to be eventually known.

Therefore, as far as we know it is harmless. Hence why I said exactly that in my original comment.

That would be understandable to commenters ITT if they knew how to read instead of satisfying their dopamine systems with a reactionary outburst straight from the amygdala against a strawman they conjured up in their head, unwittingly making fools of themselves supporting such petty and pathetic authoritarian paternalism.

And additionally, in my personal opinion - it makes plain sense that the longer we study vapes, yet find no harms, the probability increases that they are indeed harmless.

Or at the very least I believe they are no more harmful than the harms caused by our existing standards for e.g. air pollution, in that hypothetical - vaping causes no excess deaths, but may do so if we had cleaner air and lower base rates of lung disease to begin with. Then we may notice increased rates of lung disease and find an associative link, therefore speculate that there is lung disease to which vaping may be some contributing factor and may always have been, but may simply be too minor to notice at present, for instance because people affected by it die of unrelated illness like cancer before they die of any vaping-caused illness or because the lung disease vaping contributes to is also caused by something else more directly that the general population is exposed to, e.g. microplastics or dust particulates from car tires/asphalt.

I'm not an expert nor do I think the above two paragraphs constitute a fact, and I'm more than happy to change my view given sufficient reason, however I also dont think things for no reason or purely because it serves me or brings me some sort of comfort of a lazy mind. Frankly I doubt I would stop using nicotine even if I knew vaping was directly harmful in some way any more than I would stop using alcohol already knowing that it is incredibly harmful (not that I drink alcohol, but that's besides the point, I don't do it because I don't like it's sedative effects, not because of it's harms to long term health outcomes).

My reasoning for this is that even with the extremely primitive understanding of both the scientific method and the human body (not to mention technology for the analysis of it), cause and effect around tobacco-caused illnesses was known since the 1700s.

https://en.wikipedia.org/wiki/Health_effects_of_tobacco

You can check the sources yourself, but for example:

Overview of the history: https://onlinelibrary.wiley.com/doi/10.1046/j.1440-1843.2003.00483.x

Here's from the 1800s: http://w3.biosci.utexas.edu/prc/lincecum/pages/Nicotiana_tabacum-notes.html

Here's a note of observations between the late 1800s to 1920s

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3490543

“As far as we know they are harmless”

Doctors in old timey days giving people cocaine for their babies toothache.

They didn't exist in the 90s.