Thank you very much for this simpler explanation, I couldn't quite grasp the concept 100%. This also gives me a very easy way to explain this concept to others in a non-technical manner.
I realize I am super late to this discussion, but I would like to state (since I found no other comments mentioning it) that this fallacy is very close to begging the question. Using the example of "MLK Jr. is a Criminal", the arguer is relying on the definition of criminal as a member of the set of bad things to make their argument.
Example Argument #1:
1. MLK Jr. broke a law
2. "X broke a law" <=> "X is a Criminal"
3. MLK Jr. is a Criminal
4. "Y is a Criminal" <=> "Y is Bad"
Therefore, MLK Jr. is Bad
The same argument can be made in less steps, but will be met with controversey.
Example Argument #2:
1. MLK Jr. broke a law
2. "X broke a law" <=> "X is Bad"
Therefore, MLK Jr. is Bad
In the second case, it is more obvious that one of the premises is essentially the conclusion to the argument. Perhaps this is the desired solution to showing this argument is invalid in common speech.
Example rebuttal to "Example Argument #1":
"Wait, are you claiming that everyone who breaks a law is necessarily bad? Isn't that the argument you are trying to prove? You can't use your conclusion as evidence. Anyways, what about <Insert counterexample that is hard to debate>, are they bad because they broke the law too?"
I want to go on the record† as saying this isn't a directly comparable situation. Lord Kelvin believed there was no way to get more information about life, but many people today believe there is more to discover about consciousness, just that it is beyond the current capabilities of our tools. We know how to explain lots of things about consciousness, but disagree on interpretations. Kelvin said, essentially, that there was no way to draw any meaningful conclusions about life, but that it was an atomic idea, unable to be split further.
† I do this so that we don't seem to be the Lord Kelvins (w.r.t. elan vitae) of consciousness when people discover more in the future.
Wow. I also will not give anything away, but I agree that this is an insane round of this game. There are two agents with very different modeling processes trying to achieve the best outcome for themselves, but (I don't know if this applies only to me or to others), unlike a normal PD, we are not a participant so we don't know the processes of any of the agents, which makes it very enjoyable. This round is a testament to something, that is for sure.