Oh it's possible, sure. But considering that Sagan was an
   astronomer. The guy that gave the big speech was famous in
   astronomer circles - I forget his name atm - but he was the
   president of the Canadian Astronomy society in 1916 and I guess
   kind of a big deal to them. He probably read it in his travels,
   forgot about it, then it came to him as if his own. Or maybe it
   was coincidental - that's always possible. I've had ideas where
   I didn't know the source and they were my own - and then come to
   find out someone else thought of it before me. Sometimes I could
   figure out where I heard it long ago. Sometimes I couldn't.
   Either way, it's still "mine" but when I can find an older
   source I just have to admit that I just wasn't the first. == I
   even made this to remind myself to stay as intellectually honest
   as I can. The thought of one of my heroes possibly lifting
   someone's words for his own (intentional or not) reminds me to
   always trace the sources of concepts that I believe are my
   originals, and give credit where credit is due when I can.
   [1]starstuff

References

   Visible links
   1. http://icopiedyou.com/wp-content/uploads/2016/01/starstuff.jpg