:grumpy: I went to great lengths to avoid the very kind of faulty analogy.Come on don't give me that mumbo jumbo. Regardless if we can observe it or not, that does not mean it is not happening. Tree falls in the wood, no around to hear it, does it make a sound? Of course it does.
Is the cube in intergalactic space oriented "upwards"? Upwards is a term that, by definition, is relative to some other reference point. Without a second reference point, 'up' has zero meaning.
So, to be clearer in the phases explanation, remove the word observer. Replace it with external reference point. Now:
A phase is an angle (New, Crescent, Half, Gibbous or Full - or 0 through 360 degrees).
An angle occurs between two intersecting lines. If you only have a single straight line (say, the line of Sun > Mars), there is no angle; it does not exist. Only by introducing an external reference point do you have an angle (Sun > Mars > ref point). Only then is it meaningful to talk about New, Crescent, Half, Gibbous or Full or any degree in between.
A phase is a direct property of exactly three points. There must be three.