"Ne" without a "pas"

Do you notice anything strange about the use of ne in this sentence from our video on deep-sea creatures?

Ils vont servir de sujets d'étude aux scientifiques...

They will serve as test subjects for scientists...

avant que leurs enseignements ne soient exploités par l'industrie.

before their lessons are exploited by industry.

Captions 21-22, Le Journal - 2000 mètres sous les mers
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You might be thinking that the narrator made a mistake by leaving out the pas in the phrase ne soient exploités par l’industrie. But actually, adding a pas to this sentence would completely change its meaning (and make it nonsensical). What’s going on here? The ne in this sentence is called a ne explétif (also known as ne pléonastique). Instead of negating the clause (as it does when combined with pas, plus, personne, etc.), this ne emphasizes the general feeling that the clause expresses. So the phrase ne soient exploités par l’industrie doesn’t mean “are not exploited by industry,” but something like: “are exploited by industry (which would be bad).” The ne here does not negate the phrase, but rather highlights its negative connotations.

We find a similar case in our video about avian flu:

Exemple, avec une petite astuce

For instance, with a little trick

pour éviter que votre chat ne rapporte des oiseaux indésirables.

to keep your cat from bringing home unwanted birds.

Captions 19-20, Le Journal - La grippe aviaire
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As French learners, upon first glance we might be fooled into thinking there is a trick that prevents your cat from “not bringing” unwanted birds home (thus forcing him to do so), but the fact that ne is not coupled with the usual pas (nor rien, personne, plus, jamais, etc.) clues us in that this is quite likely another example of ne explétif (which it is). The ne is emphasizing the idea that we want to prevent such creatures from being brought into our parlors. This emphasis is too subtle to find a place in the English translation. We very often find the ne explétif used after “unequal” comparisons, those in which one thing is NOT like the other.

Have a quick look at this example from our video about life in the trenches during World War I:

Ces soldats... ressemblent plus

These soldiers... are more like

aux combattants du Premier Empire, des guerres napoléoniennes...

fighters of the First French Empire, of the Napoleonic Wars

qu'ils ne nous ressemblent... à nous.

than they are like... like us.

Captions 5-7, Le Journal - La vie dans les tranchées
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