I always find these arguments that appeal to ignorance boring and remind me how to lose a debate contest back in the day. Appeals to ignorance, where ignorance stands for "lack of evidence to the contrary," as in that vaping may be proven some day to be harmful, is a fallacy in informal logic, or so how I was taught. It asserts, for example, that a proposition is true because it has not yet been proven false. This is a false dichotomy in that it excludes a third option, which is that there is insufficient investigation, and therefore, insufficient information to prove the proposition to be either true or false. It also excludes the possibility that the information might remain unknown between true or false (certainly a likelihood in medicine), or that the proposition may be unknowable (certainly a probability in medicine). I remember in debate class, we used appeals to ignorance to try to shift the burden of proof to the other guy, i.e., "You can't say it's harmless just because it hasn't yet been proven to be harmful."
The reason this whole line of reasoning is fallacious, misleading and confusing is that while we may never find out if vaping is harmless (relatively so), you can still have good reasons for thinking that vaping is probably not harmful. In the case of vaping, the fact that the ingredients have never been shown to be harmful when used "as prescribed," is what some would call pragmatism. Since all the ingredients in vaping have previously been proven to be safe, as evidenced by their designations under US Food Grades and/or approval by the FDA, the transposition rule of inference in classical logic is to conclude that vaping is harmless, or at least as harmless as the FDA thinks the ingredients are. In other words, if vaping ingredients have been used safely without negative effect, the absence of a negative effect in vaping these ingredients thus far, IS EVIDENCE of the absence of a negative cause. Think Occam's Razor, or simplicity over complexity.
These arguments ignore the fact, and difficulty, that some true things may never be proven, and some false things may never be disproved with absolute certainty. The phrase "absence of evidence is not evidence of absence" can be used to further the ignorance fallacy, "the harmlessness of vaping has never been absolutely proven and is therefore certainly false." Most often it is directed at any conclusion derived from null results in an experiment or from the non-detection of something in that experiment. In other words, where one researcher may say their experiment suggests evidence of absence of harm with and/or from vaping, another researcher (with an agenda?) might argue that the experiment failed to detect the harmfulness with and/or from vaping for other reasons, and argue that "we need more experiments and more science to prove it conclusively." In othe words, our current state of affairs.
It is a well-known fallacy in these types of discussions to draw conclusions based precisely on ignorance, as in this case about potential unknown future harm from vaping, since this does not satisfactorily address, while it simultaneously ignores, the issues of burden of proof. But null results are not ignorance and can be used as evidence to achieve a given burden of proof. In othe words, again, the fact that we have not found harm in vaping, thus far, IS EVIDENCE THAT VAPING MAY BE HARMLESS (relatively so), and NOT evidence that it "might" be harmful. This isn't a matter of conjecture or perspective, it's a matter of fact using responsible thinking and reasoning. The counter argument is, "Pigs might be able to fly, we just haven't detected it yet, after many efforts to do so." This is what we are up against, i.e., a clear agenda from the ANTZ.
Again, the fact that we haven't found vaping harmful is comforting, not worrisome and troubling. Think about it.
Edit:
I need my coffee now...
