Zippor

For example, Tetris is a game without any progression at all.

In fact I would like to post this question to everyone. Whats horizontal progression to you?

Yes, it's valid. It's called a thought experiment. In fact, you can compare two fake events. Example: let's say you are near some train tracks (let's say two meters away). A train is passing by at high speed. That is one event. Another would be the same tracks, same train, now you stand on the tracks. It's obvious what would happen in each case, and what caused your demise in one of the cases. The train? Well, yes and no. In this example, the changed variable was your position, so you stepping onto the tracks was the cause. What XP (and maybe you) are saying is that it was maybe the train that killed you. Yeah, in this case, in a way it was, huh? But then again, the train was there in both cases, and in one of them you didn't die. Of course, standing on the tracks when the train isn't present is perfectly safe, but that is immaterial because it is not the two cases that we are considering.

Disclaimer: I do not advocate standing on train tracks. It's up to you though.

I cannot control for example the RNG, but that doesn't matter. If I had been wearing exotic armor, the RNG would still have spit out the same numbers at that moment - unless armor type is used as feedback to the RNG. I don't think it is.

Because I'm comparing it with how it would have gone down if I was wearing full exotics. I'm not comparing it to how it would have been if, for example, I would have fought without any gear whatsoever.

Correct, 10140 health would be a combination of different things, but the point is that we are comparing it to the case of 10000 health. Since this is just an example, let's assume that 10000 health is the absolute maximum one can achieve without ascended gear, and 10140 is the maximum with ascended gear.

And yes, since we are comparing the case of 10000 to the case of 10140, the additional 140 health is actually due to the changed variable, in this case, ascended gear, or ball 171, as you wish.

The "evidence" is not incomplete, because no other variable matters. My opponent would have worn what he was wearing regardless of what I was wearing. If he had a bad build he would have had that bad build regardless of what I was wearing. If he was lower level he would be lower level regardless of what I was wearing. If he made mistakes or even were unlucky, he would have made mistakes or be unlucky regardless of what I was wearing. It's true that single instances doesn't give statistically meaningful data, but that is beside the point because we are not talking about the general case, but about this particular fight.

The statistics are not insufficient for my argument, because my argument is not that ascended armor affect all fights (it does, of course, but I'm not basing that on the outcome of that one fight). My argument is that I would have lost that fight without ascended armor. This has nothing to do with statistics because we are talking about a single instance.

My argument is not circular either. The base case would be that I was wearing exotics. The change was that I was wearing ascendeds. The result was that I won, but with such a small margin that it has to be because of the change. The decision to wear ascended armor is unrelated to any other event that would affect the outcome of the fight, and therefore it is not cherry picking (which has nothing to do with circularity), but instead identifying the reason for the win.