Necessary Thing

[Angrboda]

We don't know whether anything is necessary in the sense that it would be an impossibility for it not to exist.  I don't think we have any way of telling whether some thing's existence is necessary.  Therefore postulating some thing's existence as necessary is pure assumption.

Fair enough. Do we have any way of telling whether or not some thing's existence is non-necessary (i.e. contingent or conditioned upon some other thing)?

If something stops or starts existing, that would by definition be contingent. I'm not familiar enough with QM to suggest we have any examples of such, but it is commonly claimed that we do have such examples. Stating whether ordinary matter ever stopped or started existing is above my paygrade.