And just how is consciousness relevant to this thread?
Please demonstrate the existence of this thread, as something that is totally independent of any consciousness.
In other words, you cannot avoid consciousness (including an indirect agent of it)whether you are doing mathematics or not.
It is simply impossible. Since it is impossible you have no choice but to be aware of it when you are doing mathematics
What does it have to do with your assertion that a set is the union of its members?
Since a set and a member are no more than the reflection of the mathematician's consciousness, it is essential that the mathematician's consciousness will be aware of the fact that its results are nothing but its own reflection.
This is known as the minimal test that checks the intelligence of any creature that enables to get its own reflection in some reflector (some mirror).
You put it in front of a mirror. If the creature does not recognize its own reflection and look at it as another creature, then it does not pass the minimal test of intelligence.
The current community of mathematicians is a group of persons that are trained for the past 2500 years to ignore their own reflection, until they really think that their own reflection is an independent object.
You may say: but what if this is not the mathematician's self reflection, but really a realm that is totally independent of us?
In that case another question arises, which is:
Who you are able to know that there are things that are your own reflection, and on the same realm there are things that are not your own reflection?
In other words, how these two alternatives can be compared with each other, without any common basis?
If you think about it you cannot avoid the conclusion that things are the result of Symmetry(the invariance and the common)\Asymmetry(the variance and the non-common) complementation.
Without this complementation nothing is researchable.
A set is a researchable thing, and it is a researchable thing exactly because it is not less than the common(what you, by mistake, call a set)\non-common(what you call a member) complementation.
Since any researchable thing the result of some complementation, and since a set is a researchable thing, its members are inseparable of it and it is not less than a one thing with many faces (an organic realm).
Again:
Without this complementation no two things (abstract or not) are gathered into a one thing, and no system that is beyond its atomic state (total unification or total isolation) can be found.
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X={{A,B},{A,C,D}}
There is nothing in {A,B} or {A,C,D} which gives us the knowledge that {A,B} or {A,C,D} are also members of X.
This knowledge is available only if {{A,B},{A,C,D}} exists.
So, a member of X has a meaning only by {{A,B},{A,C,D}} and this knowledge cannot be related to {A,B} or {A,C,D} without the knowledge of {{A,B},{A,C,D}}.
In that case {A,B} U {A,C,D} does not have any knowledge of {{A,B},{A,C,D}} unless it is used as a hidden assumption of {A,B} U {A,C,D}.