It’s a quote from Francis Bacon, a rough translation I’ve found is “Real knowledge lies in knowing causes”. It’s been a while since I’ve taken latin, though, so I can’t quite confirm that, but it sounds close.

Also attributed to Aristotle, I should say, in the greek as “Scire est per causa scire”. And a more formal translation is “To know truly is to know through causes”

Almost. the literal translation is: Truly to know is to know through their causes.

There’s no “their” there.