I guess I worded that poorly; it isn't merely that we don't need an objective measure: we literally don't need a measure at all, as the crime would be attempting to cause it, whether or not it was even possible to do, and so we simply do not care if the activity was addictive. If you are going out of your way to exploit the psychology or physiology of other humans in an attempt to use that to sell your product, maybe that is what should be illegal.
This would then mean that "our expert witness has strong evidence that my client's product area is not 'addictive', so my client could not ever be said to be engineering addiction" would not be a defense any more than "the plan my client came up with to kill their alleged victim could not possibly have worked, so my client can not be charged with attempted murder" is (at least generally, afaik) not a defense.
Ok, fair, so, to try to apply this to my analogous crime: I would agree that attempted murder does need a definition of "murder"; but, the crime does not care whether your specific plan would have led to an act of murder, only whether or not the defendant was trying to murder.
We thereby do not necessarily need a way to know whether reading--either your book or any book--is addictive or not, but only the extent to which you were going out of your way to make it addictive, for which I think it might then be OK to have some specific-yet-contrived definition that is difficult to apply to any specific product but feels like a wrong thing to do (maybe my "exploit human psychology or physiology")?
The above phrasing, an attempt to "exploit the psychology or physiology of others", works fine. It's a form of fraud, or scamming. Is an attempted scam a crime? I guess probably not, oh well.
I don't believe devices are addictive, but that's irrelevant to Satya Nadella believing it and trying to exploit it and thus being a scammer.
It's going to get fuzzy around whether entertaining somebody counts as exploiting their psychology. Obviously it doesn't, but that would rest on reasonably assumed consent.
※ People do get sentenced for attempted fraud, but that's for more blatant things like trying to extract money from an unwitting victim's bank account, rather than just saying "we must figure out how to commit some fraud".
This would then mean that "our expert witness has strong evidence that my client's product area is not 'addictive', so my client could not ever be said to be engineering addiction" would not be a defense any more than "the plan my client came up with to kill their alleged victim could not possibly have worked, so my client can not be charged with attempted murder" is (at least generally, afaik) not a defense.