Systems

A system is nothing more and nothing less than a set of relatively stable interactions.
A system can be evaluated only from the outside.
A system exists only in the mind of the observer.

I’ll discuss these three affirmations from the bottom.

Even if the objects that compose the system exist ‘in the real world’, the system itself exists only in the minds of the observers – the person who had first identified the interactions and all those who agree with him.
To illustrate my point I’ll give you three examples.
–  A constellation is “a group of stars that forms a particular shape in the sky and has been given a name“. A long time ago, when those constellations had been named by our ancestors, people thought they were something totally different than what we think of them now. Yet they continue to exist as before and are identified using the same names.
– The Solar System. It works totally different today than it used to during Ptolemy’s time…
– The human body. Each of us temporarily inhabits one but we still don’t know exactly how it works or whether, in reality, it is but a small – and not even autonomous, part in a way larger system.

No system can be evaluated from the inside.
Apparently this is pure nonsense. I have just said that each of us inhabits a human body, which is a system by itself. Yeah, right. And when was the last time when you have fully understood how your body works? Or when any of us was able to do that… including here the doctors in the audience – exactly those people who do understand the meaning of “A physician who treats himself has a fool for a patient.” …
On the other hand, most of us – at least after a certain age and before dementia takes over – are ‘house trained’ and relatively polite. Because of our consciousness? Something that we hardly understand and sometimes think of as being somewhat separated from our ‘mortal’ body? Please remember, in this context, that some of us consider our souls as belonging to somebody else…

A system is nothing but a relatively stable set of interactions.
That have been either identified or established by us. The Solar System has been identified by us while the GPS (the Global Positioning System) was designed, and build from scratch, by us. Composed of materials found in the Solar System and obeying the same ‘laws’ as the rest of it but, nevertheless, something different. And to understand what I mean, please imagine for a moment that gravity would suddenly become a much weaker force. Big enough to keep the Earth together but not big enough to maintain Earth’s current orbit, at Earth’s current speed around the Sun. Nor big enough to keep the Sun together… Depending on how weaker the gravity would become the planets would scatter away while the Sun would become nothing more than a nebula… or, if the gravity would become reality small, it would be possible that the gases furiously escaping from the Sun would catch at least some of the planets from behind and melt them into a lot wider nebula….
Or, alternatively, imagine that the GPS satellites run out of power and no longer emit any radio signals. They would continue to orbit the Earth for a while but the GPS system would have been gone the minute when too few satellites would have remained active …