I very often hear scientists talking about how according to modern theories it's completely possible to something manifest out of nothing, and therefore there is nothing illogical of saying that universe came out of nothing. How is this 'nothing' defined and trough what logical process? Very often i hear scientists explaining this 'something out of nothing' with an argument that in this 'nothing' particles pop out to existence spontaniously, some "branes" collide sometimes starting new universes, etc. But that is not 'nothing' to me. To me, 'nothing' means absolute nonexistence = no space, no random events, no branes, no nothing. Which is very problematic concept philosophically because just saying that "nonexistence is absolute" gives the nothingness a definition which questions it's nonexsistence. And, if nonexistence itself is nonexistent, then the opposite, the existence, must be true, and if nonexistence exists then it's again existent, and there is 'something' rather than 'nothing'. Ofcourse that is just my own philosophy, but for certain a state where branes and random events do exist is not 'nothing', unless 'nothing' means just absence of matter. Is the 'nothing' just a name for a pre-state of the existence where anything we know did not yet exist, or does it mean a true 'nothingness'? How is this pre-state, whatever it is, defined? I mean, how is it even theoretically possible to define it if we assume that nothing that we know didn't exist?