Did Carl Sagan Libel Christiaan Huygens?
I came across a reference to this claim in an online conversation and got curious enough to google for it. All of the references I found were suspiciously similar, suggesting that they all were based on the same source. I eventually concluded that the source was Sagan. None of them provided any evidence for the story in anything Huygens had written.
So I want looking and found a webbed translation of Cosmotheoros, a treatise on matters astronomical written by Huygens late in his life. It's an interesting work, combining what appears to be an accurate account of astronomical knowledge of the time with lengthy speculations about possible inhabitants of other planets. Huygens, living more than a century before Darwin, takes it for granted that living creatures are the result of divine design and, logically enough, tries to figure out whether and how a benevolent God would have populated other planets. That seems a bit odd to the modern reader, but the author makes it clear that what he is offering is speculation. There are lots of references to Jupiter and one to hemp, but nothing that even comes close to supporting Sagan's story.
Huygens writes, with reference to Jupiter and Saturn:
"This Position of the Moons, in respect of their Planets, must occasion great many very pretty, wonderful sights to their Inhabitants, if they have any: which is very doubtful, but may for the present be suppos'd."
Which does not sound like a statement from someone with the view of the subject that Sagan attributes to Huygens.
I see three possibilities:
1. I have somehow missed, in Cosmotheoros, the passage on which Sagan bases his story. I think that very unlikely; I haven't read the whole treatise, but it is webbed with a search engine.
2. Sagan is accurately reporting something Huygens wrote elsewhere, perhaps a theory he had rejected by the time he wrote the treatise.
3. Sagan's story is false. Either he is deliberately lying for the sake of telling an entertaining story about how foolish people were in the past or he never bothered to check something he misremembered or got from someone else.
I favor alternative 3, but perhaps one of my readers can provide evidence for one of the others. If the story is based on something Huygens wrote I suspect, after looking through Cosmotheoros, that Sagan is misrepresenting a speculation as a claim.