Re: the big bushcraft question
Hmm, a deserted island is deserted for a reason. No food, no water, or it is always in line with typhoons or something. There has to be a good reason though. That said, it depends on climate etc., as to which tool is most important.
So, in the tool department, if it's a tropical island, I'd want a cutting edge. Whether it's stone, glass or a modern knife doesn't matter. If it's a cold northern island, I'd want fire.
Then in the natural resource department, fresh water. Can only go a few days without fresh water.
All life is subject to the laws of Nature, or to be more precise, the laws of our CREATOR.