PKD on mescalin insights behind "Flow"

From two different letters around August 1970

"I have just finished the rough draft of a new, long, s-f novel, FLOW MY TEARS, THE POLICEMAN SAID. {...} I've reworked it and reworked it; I rewrote the final section seven times, plus holographic changes. At one point in the writing I wrote 140 pages in 48 hours. I have high hopes for this. It is the first really new thing I've done since EYE IN THE SKY. The change is due to a change that overtook me from having taken mescalin, a very large dose that completely unhinged me. I had enormous insights behind the drug, all having to do with those whom I loved. Love. Will love.
    
...

    With acid I never had any genuine insights, but on mescalin I was overwhelmed by terribly powerful feelings – emotions, I guess. I felt an overpowering love for other people, and this is what I put into the novel: it studies different kinds of love and at last ends with the appearance of an ultimate kind of love which I had never known of. I am saying, "In answer to the question, ‘What is real?’ the answer is: this kind of overpowering love.["]"

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