Starting when he was forty-five years old, and continuing from February 1974 for the last eight years of his life; Philip K Dick had many religious experiences; which became the focus of his thinking and writing in his last novels and the philosophical notations and letters than have survived as the Exegesis.
This can be understood as a specific example of one of the many ways that God can work to stimulate a man to orientate towards Jesus Christ (i.e. salvation, after death), and to learn spiritually during this mortal life (i.e. theosis).
PKD's experiences led to a conviction that he was receiving a mass of vitally important information, and the Exegesis records some of his struggles to understand and "deal with" this deluge of incomprehensible input.
This involved casting-about widely, reading and talking, following hunches, seeking appropriate and adequate concepts, trying out multiple hypotheses: and writing, writing, writing...
The "conventional wisdom" is that PKD was engaged in wild speculations, circular or self-contradictory notions; was chasing a will-o-the-wisp - and that, in the end, he failed to reach any valid destination.
But I suggest that - understood in an ultimate sense - PKD was doing pretty-much what God hoped he would do, and that very likely he did achieve a great deal of what he most needed to achieve at the spiritual level.
God's intent with some men - perhaps many of us - is to galvanize us to to active spiritual work; orientated-towards God, Jesus Christ, and divine creation - and to learn from this process by trial-and-error.
The terminus of such a process is not some version of "enlightenment" in this world... of unending bliss without experienced suffering...
Nor is it achieving a settled and complete understanding (which, after all, could only be a grossly simplified model of reality)...
Instead; the terminus aimed-at is our mortal death and that which follows thereafter.
The divine intent (I infer) is twofold: To point us towards salvation; salvation being that we embrace the gift of resurrection offered by Jesus after our death.
And further; before our death - during this mortal life to gain spiritual learning; learning that will accumulate to benefit our divine-self-to-come; that is, after salvation. This learning from the experiences of mortal life is theosis - because it results in (eventually, not during mortal life) becoming more God-like in our nature.
This theosis-learning during mortal life needs to be understood in a spiritual sense, because it is not about memory - and is indeed not affected by the brain, body, decay, disease, death or any material circumstances that follows after the spiritual learning.
Even if what we have learned is immediately forgotten - in this-world, in a material sense; nonetheless, if it is significant for our eternal resurrected and Heavenly life - it is spiritually retained, potentially for eternity; so long as salvation is embraced in the end.
My interpretation of Philip K Dick's eight years of changing his mind, trying-out innumerable bizarre notions, following multiple blind-alleys, making many mistakes - as well as having transcendent insights, and (briefly) achieving Christian certainties - can therefore best be understood as a valid and appropriate response to his mysterious, perplexing and God-given experiences from February 1974.
Some would say that God 'ought' to make Himself clear. That God would not really operate in ways that are confusing or ambiguous. And that Men ought to be aiming at some settled and clear and correct understanding.
Yet, surely it counts as a major success for God; that from early 1974, PKD uprooted and re-orientated his life; that he worked many hours of most nights at his self-imposed task of understanding his spiritual experiences; that he focused (again and again) on understanding Jesus Christ - His real nature, His goals on earth and in Heaven...
What seems in this-worldly terms to be just thrashing around in philosophy and theology; at times being plagued by obsessive or even psychotic preoccupations; at times making bad lifestyle choices; afflicted by wide mood swings -- as well as experiencing extreme joy, considerable serenity, performing acts of loving kindness, laced with self-deprecating humour, and much else that is positive...
What seems to be misplaced activity or avoidant behavior according to a pragmatic interpretation; may be, in an ultimate sense, not-far-from being the best possible life attainable by the actual man Philip K Dick; given his innate nature, abilities and limitations.
That is: a life of spiritual learning (theosis) enriching the final choice of disposition with salvation.