What delighted me about Heinlein was the individuality of his voice.  Nobody else sounded quite like him. 
     I liked the confidence with which he wrote, his breadth of knowledge, his clever turns of phrase, and the way he had of slipping necessary information into his stories sideways. 
     Beyond that, Heinlein offered me a special education in the relativity, arbitrariness and transience of common social practices we ordinarily take for granted as solid, real and enduring.  As Heinlein put it in a talk in 1941:  "Any custom, technique, institution, belief or social structure that we see around us today will change, will pass, and most of them we will see change and pass." 
     When the narrator of a Heinlein juvenile newly returned from the stars is shocked by social change and recalls his father's disapproval if one of his sisters came to the dinner table without a hat on her head -- "head bare-naked, like an animal" -- that made an impression on me.  In the conformist Fifties, it was a useful thing for a youngster to know that things do change and could easily be different than they were. 
     And were going to be different, too. 
     Above all, however, what I valued most in Heinlein was a handful of stories that first frightened me, then intrigued me, and ultimately challenged me. 
     There was Beyond This Horizon , which asked in so many words:  "What is the meaning of life?" 
     There was "Waldo", which said that the world is constructed out of our beliefs, and alters as our beliefs alter. 
     There was "Universe", which said that the human situation is not what we think, that we've forgotten our purposes, and that we need to be shown where we are and where we're going. 
     And there were the other unsettling early Heinlein stories -- "They", "By His Bootstraps", and "The Unpleasant Profession of Jonathan Hoag".  In these stories, it wasn't just social convention that was called into question.  It was the very fabric of assumed reality. 
     That gave me something to think about. 

     The first paper I was asked to write during my freshman year at the University of Michigan was for an introductory psychology course.  The teacher told us to do some investigation and compare the representation of a piece of psychological research in the popular press with what psychologists themselves had to say about it. 
     I saw this as an opportunity.  In several of his stories, Robert Heinlein had cited a man named Samuel Renshaw as the source of techniques for training vastly improved accuracy of perception.  I could find out for myself what was fact and what was invention. 
     I received an A for the paper I wrote, and I sent a copy of it to Heinlein.  This time he answered me with a three-page single-spaced letter. 
     That was a long time ago, and I no longer have the letter.  The one thing that I do remember from it now is Heinlein saying that when he was working on a manuscript he was able to remember it so well that he could lie awake at night and mentally make changes in punctuation.  But when he was done with a story, he could forget it so completely that he could read it at a later time for pleasure. 
     In 1966, when I was writing regularly for fanzines, I put this paper through the typewriter, and then passed it on to British fan Pete Weston.  He published it as the October 1966 issue of his apazine Nexus .