We live in the world of Effects, without ever seeing the world of Causes. Division entered and this was the Fall. We divided off from the divine part of ourselves and have ceased to even know it. Instead, we live in the world of shadows, obsessed with duality, and seeing no further than our senses permit. The way back is guarded by an angel with a flaming sword, because the attainment of eternal life is impossible as long as we remain mired in temporal earthly things.
Nothing mired in an earthly consciousness can have any share in eternity.
At yet another level, the reality we see around us is the direct result of our individual karma, the group karma of our race and nation, as well as the collective karma of humanity. Life is a huge learning arena, set into play by ourselves for ourselves in order to stimulate our own awakening. However long it takes for this to occur is precisely how long it WILL take for each and every one of us. From an earthly perspective, it clearly does exist and possesses certain objective truths that we can agree upon that can be measured. Yet, even at the earthly level, the universe can be rightly called illusory in the sense that all is not as it appears.