Survival is the main theme, which will be experienced through both game mechanics such as combat/survival mechanics and content such as PC-NPC dialogues/illustrations (How should it be experienced through these "devices" in a game?). You wrote specifically "survival mechanics" in your comment, thus, I replied that mechanics and content complement each other. Here, somehow, you are mixing "mechanics" and "theme" although the word is clearly written in the post I referred to. Also, if you check out the info, you will find the diversity of characterization of NPCs and dialogues are one of the focuses of the project as well as turn-based combat mechanisms.
In any case, if anybody has any doubt on my comments or any other person's comments here, he is free to check it out by himself. In the forum and/or Kickstarter page, he can check it by himself since the info is pretty open.
I wrote survival mechanics because it is part of the vocabulary used to depict the game. Here for one example among others
http://www.vg247.com/2012/06/07/troika-veteran-heads-zombie-rpg-kickstarter-effort/
And second point, you wrote that survival mechanics are tied to dialogues under the theme of human condition.
And later, you wrote that survival is the main theme.
Human condition can be one of survival. It can be not altogether. I mixed nothing here. I could not have guessed that you would substitute the theme of human condition with the theme of survival in a later post.
More on that, it is irrelevant: a theme does little to determine a game experience.
The theme being about survival is not enough to deliver a gameplay supporting a survival experience.
Game mechanics are the primary content of a game. Any game. It brings no light to write that mechanics and content complement each other.
A story, a setting whose theme is survival is not enough to deliver a game experience of survival. A game whose theme is survival and featuring no survival mechanics is unlikely to deliver a survival experience.
Games are a second hand experience through an avatar. Emerging an avatar into a world struggling for survival without applying any survival mechanics delivers no survival experience.
All this to be back to the starting point: which one is subordinated to the other? The story? The survival mechanics?
Telling that the theme is survival solves nothing. Every game set in survival settings has survival as theme, it does not make it a game delivering a survival experience.
And people wishing for a survival game are not in the same boat as people wanting a game set in a surviving world.