We know of existence by our mind. If we are not alive, no one can know of any existence. Existence, the word itself, the idea, springs from the mind. There can be no existence without a mind. The very idea comes from the mind.
When we say that it can exist even when we are no more, when there is no mind, we are projecting our mind into the future, it is mind again. It is mind which begets the very idea of existence. This idea of existence is in the mind-I am. Since existence and mind are inseparable, there can be no existence without a mind.
Source: Why Do Civilizations Fail? http://www.kundaliniresearch.org/why_do_civilizations_fail_4.html
Contributed by: ~C4Chaos