But I'm not making any assumptions. I know of the existence of something (and can easily prove it), but as far as I know I have never come across nothingness, or ever seen anything to suggest it's existence is possible. You are making the assumption that nothingness is a possible state. For me to answer the question, you'd have to first show how it could be so.
Some speculate that outside of this universe we have nothing, are they automatically wrong because they cant show it to you? Some pantheists
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speculate that consciousness is in everything, including rocks & stones. Are they automatically wrong because they cant show how it could be so. If there is something, then I can imagine that its possible for their to be nothing
If you can have something, then we can surely understand nothing i.e. something - something = nothing. Or take my earlier example in this case for non-pantheists, when a being dies its consciousness level changes to 0.
I am not wondering if something can turn into nothing in any case. I personally dont think it can, and we have proved this with energy in closed systems. I am only wondering why the default state isnt nothng to begin with, in which case we would still have nothing now.