Perspectivalism has me looking for thirds to every old dichotomy. There is a perceiving subject for every fact/value distinction, and a moral actor who decides between deontology and teleology. Frame and Poythress articulate this triad as "subject, object, norm."
Who is this "subject"? Does the "subject" really make any difference to what we know and do? Is the "subject" important enough to sit side-by-side with physical reality and natural law?
Rene Descartes brought the "subject" into the center of this philosophy when he said, "I think, therefore I am." The observing self provided the first fact for Reason (the norm), which used it to deduce Reality (the object).
Descartes left the "subject" behind once he got his feet on the familiar ground of philosophy, but his younger contemporary Blaise Pascal had more interest in the "subject." Pascal, who said, "The heart has its reasons of which reason knows nothing," is often claimed as a forefather of existentialism.
I'm not ready to write about existentialism yet--although I delight in the great "Christian existentialists" (Pascal, Kierkegaard, and Dostoevsky), I could never force myself to take existentialism itself seriously before Frame and Poythress showed me how. So let me jump to something that I actually believe in--quantum physics.
In the weird world of quantum physics, what we think of as "reality" is arguably less real than the observing self. Twenty-first century scientists believe the laws of physics govern time, space, matter, and energy, but this does not result in a single predictable world. Instead, physical realisty and natural law produce a "wavefunction of the universe" which includes all possible worlds. The "actual world" that you and I observe is a collapsed subset of that wavefunction. Most quantum physicists say the act of observation causes the wavefunction of possibility to collapse into any one actuality.
Who is this Observer? Does the subject matter? And should I master existentialism or quantum physics to find out?
I feel like Odysseus, sailing between Scylla on one side and Charybdis on the other.
But if Truth lies on the other side, I must sail on...