Navigation and Approximation
To navigate the world and our lives, we need a map of Existence. And when we are not quite comfortable with the world, it is easier if the map is quite simplified - an approximation good enough to avoid the main pitfalls, and rough enough to be simple.
A dualistic and fragmented worldview is one of these simple approximations. It works well for a while, but the inconsitencies eventually become to obvious to ignore. That is when we can open up for a more transdual and fluid experience of Existence. One that is still simplified, although maybe less so.