While at the highest and truest level, everything is a Unity, the illusion of separation that we experience in third density can be quite convincing. Part of this seems to stem from our five senses, and how our brain processes information. Another part seems to be from the basic instincts that we inherit from our second density ape-body ancestors.
Part of this also seems to be from the identity of oneself. This identity of self is also based upon the culture that we are brought up in, and its beliefs. It is also from what are parents teach us at an early age.
It does seem that second density animals have an innate awareness of the unity of all things, while not having self-awareness, and the processing levels of human brains. It also seems that the intellectual and rational mind of a human can play a role in the thought that there is a separation among things.
The free will aspect of third density also seems to play a role in possibly making the illusion of separation a more compelling thing. For instance, service-to-self individuals or groups can promulgate thoughts ad beliefs to the populace of separation. Often, this seems that it might be used as a way to gain power and control over others, for the purposes of serving themselves.
There is the well known phrase “divide and conquer”. Creating divisiveness among groups that are desired to be controlled seems to have been a method used on humanity for centuries and millenia.
Because of free will, it seems that there is an intention for some level of an illusion of separation to exist. The progression seems to be from the consciousness of early third density beings that were originally closer to those of second density, to beings of higher consciousness that can move into fourth density.
It seems that, outside interference, from groups and entities not native to Earth, has also played a factor in making the illusion of separation even greater. The channelings discuss the Orion Empire, and how it has influenced Earth in various ways.
Research also points to groups on Earth that would benefit from a greater illusion of separation. For instance, less consciousness or awareness of Unity would benefit those predisposed from war, or even benefitting from it.
Belief systems can also cause a greater illusion of separation. One could just look at the history of religious wars upon Earth.
As John Lennon wrote, imagine what the world could be like if more people had greater awareness of the truth of Unity.
As the Law of One information points out, everything, at the highest level, simply is One. Souls are meant to experience this illusion of separation in third density, no matter how strong, or thick, it might be. Souls are meant to also constantly make choices, about how they will love. Third density on Earth indeed seems a very tough school, that is also a powerful learning environment, and opportunity.