<p>The mere fact that we all must die one day already is confirmatory that we have a limited time to live in the world. You used the word "while" which is descriptive of time. Humans are made to live and die at a particular time which is not same for everybody. There are some people that their own time will be shorter than others and others' longer. So the "while" description of the time frame to live desceibes a limited time to live in the world which varies with people.</p><p>But over the years, the death trend in most countries has been estimated and we now have the life expectancy figures of every country. It is not accurate but based on established facts, this has served a great tool to be able to understand how long one is expected to live should everything go normally and under normal healthy circumstances.</p><p>So, I have not only thought about it but i do believe that all only live in this world for a limited time which varies with everybody. Death will always come knocking at our doors one day and that exact day no man knows. So, the known fact is; we do live for a while but the unknown fact is; the length of this time (the while).</p>