Nonexistence is not the same as death. Death is the breaking down of a living organism, it is the cessation of vital faculties. Death could be viewed as a process or event. Nonexistence is not a process or event; nonexistence is non-existing, it does not exist.

if you try using the definition of existence given from the seeming dictionary definition OP gave, these assertions are rendered as "That which is observed is observed because that which is not observed is not observed". What this is supposed to communicate about the meaning and implications of existence, I do not know. — MindForged

Actually the implication is closer to "that which exists can be observed because it exists, and that which does not exist cannot be observed because it does not exist".

That which does not exist cannot be observed (or interacted with). That which does exist can be.

It's not giving me a real understanfing of what you think existence is. It's like using the word "true" in your definition of truth. — MindForged

As stated above, my points are fairly straightforward. I am asserting that existence is infinite in extent, and eternal in duration. I am also asserting that we are parts of existence.

Furthermore existence is being. It's difficult to get much simpler than that while remaining coherent. You must keep in mind that human language has its limits. Many things are difficult, some things nearly impossible, to describe with words. This could be viewed as a demonstration of the human brain's limited abilities and the limitations of its concepts.

Further, existence having a beginning does not imply there was a state of so called non-existence beforehand. That's a logical doozy because it contradicts itself, but not in the way OP intended. It can easily mean there was a first moment of time. There's no "before" a first moment because "before" is a temporal concept, and clearly someone positing a first moment of existence is not positing a time before time. That's just dumb. — MindForged

The idea of a "beginning of existence", or a "first moment of time" suggests that existence just began. How would you explain that? It is essentially a something-from-nothing premise. ("No before" essentially implies nothing.)

How does something, how does time, just come about? This must be explained.

How does existence "just begin"?

Eternal existence requires no such explanation. If existence always existed there would be no event, there would be no occurrence requiring explanation.

Eternal existence is the simpler explanation. Eternal existence always exists, it does not just pop into being. Eternal existence passes Occam's Razor as it is the simpler explanation of the two. Existence "just coming about" requires further explanation, it concerns a more complicated premise and by extension a more complicated explanation to support it.

I am simply asserting that existence is infinite in extent and eternal in duration, that there is nothing other than existence, and that we are parts of existence.

Empty space is still part of existence, it is still existent just like the atom and does not serve to limit existence.

"96% of the universe is missing" is a rather confounding statement to me. How could it be "missing"? Wouldn't it have to be accounted for before it could go missing? And where did it go? What does this even mean?

Additionally the philosophy put forth here is not limited to the term or idea "universe", thus the use of the term "existence".

Following the premise of your statement, if part of the universe is indeed "missing" it must have went somewhere, and that somewhere would have to be another area of existence.

You mean you have no funds in your bank account?

You should still have "$0.00", or zeros, or digits in your bank account representing that you have no funds. In other words your account would still contain information.

Wouldn't that be something rather than nothing?

Often when we use the term "nothing" it's actually in reference to something, we just mean we have none of what is being referenced. But that isn't the same as "nothing", exactly.