Two insights, each respectively from Buddhism and Christianity, may combine to reveal something important.
The Third Noble Truth of Buddhism states that we can escape the suffering inherent in life (which is acknowledged by the First Truth).
For Christians, though humans are mortal, Jesus Christ’s example can be followed to lead a more virtuous life.
We can transcend life’s suffering by following the examples set by ideal beings: even though they are supernormal!
Plato used his allegory of the cave to demonstrate man’s attachment to the ideal forms. After spending his life in a cave, coming to the surface and seeing the sun was a new kind of experience.
In Buddhism, it is said that desire is at the root of human suffering. What if the desire for perfection–i.e., for life to take on the shape of Plato’s forms–is an example of this?
Perhaps proving the Buddha’s noble truth #4, that we can overcome suffering, consists in shedding our fantasy of becoming ideal humans. Assuming this, transhumanism and posthumanism may go too far!