In my humble opinion, PKD was grazing what the perennial philosophy offers to be the Truth of existence. To quote Waking Life:
> Now Philip K. Dick is right about time, but he's wrong that it's 50 A.D. Actually, there's only one instant, and it's right now, and it's eternity. And it's an instant in which God is posing a question, and that question is basically, 'Do you want to, you know, be one with eternity? Do you want to be in heaven?' And we're all saying, 'No thank you. Not just yet.' And so time is actually just this constant saying 'No' to God's invitation. I mean that's what time is. I mean, and it's no more 50 A.D. than it's two thousand and one. And there's just this one instant, and that's what we're always in."
Perennial philosophy is the view that all philosophies or religions are getting at the same thing, or have the same root.
That's quite different from PKD's hypothesis (one of many he entertained) that the present moment is something like a holographic superimposition on biblical times in ancient Rome.
PKD meant this quite literally, as one possibility of what reality might actually be, not as an opinion on what different philosophies or religions are getting at.
PKD posited 50AD. The perennial philosophy posits there is only one moment. Hence, the quote included in my comment. The quote explains the connection.
PKD grazed the truth but fell short, and this is alright.
Ironically, there are actually many different perennial philosophies, each of which believe different things.
The thing they have in common is that they believe all religions or philosophies are getting at the same thing or have their root in the same thing or experience.. but what that thing is differs from one perennial philosophy to another.
You seem to have cited one such belief -- that there is only one moment -- but I'm not sure what the origin of your belief is. Which version of perennial philosophy are you referring to?
I'll meet you on your terms. Let's look at Huxley.
According to his research and the works he chose to survey, what is it that one might conclude he sees as being "the single, metaphysical truth or origin from which all esoteric and exoteric knowledge and doctrine has grown?"
Just take a look at the Wikipedia article you linked to.
In it there are versions by: Huxley, Philo of Alexandria, Ficino and Pico della Mirandola, Agostino Steuco, Emerson, Blavatsky, Huston Smith, and a bunch of others.
Take a closer look at what these people believed and you'll see they believed different things (except that, again, they believed that there was a common source or experience that different religions stemmed from or were getting at).
For example, from the article, "the Egyptian god Osiris and the Greek god Dionysus had been equated as Osiris-Dionysus by the historian Herodotus as early as the 5th century BC", while "The mystic Ramakrishna's spiritual ecstasies included experiencing the sameness of Christ, Mohammed and his own Hindu deity". Not really the same, is it?
"Marsilio Ficino (1433–1499) believed that Hermes Trismegistos, the supposed author of the Corpus Hermeticum, was a contemporary of Mozes and the teacher of Pythagoras, and the source of both Greek and Jewish-Christian thought."
Again, not the same as the other two.
"Ficino saw his thought as part of a long development of philosophical truth, of ancient pre-Platonic philosophers (including Zoroaster, Hermes Trismegistus, Orpheus, Aglaophemus and Pythagoras) who reached their peak in Plato."
So now the peak is supposedly Plato, not Osirus, Christ, Mohammed, or a Hindu diety.
Then there's Steuco who believed "that philosophy works in harmony with religion and should lead to knowledge of God", but that's different from Emerson, who thought "an individual's intuition of truth was taken as the criterion for truth".
Etc, etc, etc...
By the way, in none of the above (or anywhere else in this Wikipedia article) is there any mention of what you said perennial philosophy (and, according to you, PKD) were getting at: that "there is only one moment". Where did you get that?
Perhaps a better umbrella for what I am referring to would be non-dualism.
i’m referring to Buddhism, Sufism, Hinduism, and Esoteric Christianity.
key figures would then be Patanjali, Buddha, Ramana Maharshi, Jesus Christ (Gospel of Thomas), St. Theresa of Avila, The Desert Fathers especially Anthony The Great, Shankaracharya, Rumi, and Hafez.
Patanjali in the non-dual Hindu tradition.
Buddha in the Buddhist tradition.
Jesus (as expressed in the Gospel of Thomas) representing Christianity.
Shankaracharya for advaita vedanta.
Ramana for Self-Enquiry.
Rumi, Hafez for Sufism.
also Somananda for Kashmir Shaivism.
Apologies if there was confusion in terms. It seems we were coming at it from different angles.
> Now Philip K. Dick is right about time, but he's wrong that it's 50 A.D. Actually, there's only one instant, and it's right now, and it's eternity. And it's an instant in which God is posing a question, and that question is basically, 'Do you want to, you know, be one with eternity? Do you want to be in heaven?' And we're all saying, 'No thank you. Not just yet.' And so time is actually just this constant saying 'No' to God's invitation. I mean that's what time is. I mean, and it's no more 50 A.D. than it's two thousand and one. And there's just this one instant, and that's what we're always in."
https://en.wikipedia.org/wiki/Perennial_philosophy