But when I had attained an Acquaintance with the French, Italian and Spanish, I was surpris'd to find, on looking over a Latin Testament, that I understood so much more of that Language than I had imagined; which encouraged me to apply myself again to the Study of it, and I met with the more Success, as those preceding Languages had greatly smooth'd my Way. (3.12)
Believe it or not, this is revolutionary education at work. People used to have to learn Latin first, even though it's so darn difficult, before they could learn other, comparatively easier languages. Franklin offers a theory, complete with his own experience as evidence, that it's actually easier to start with simpler, building-block languages, and work your way up to the more difficult ones. (However, Franklin's such a smarty-pants, and so committed to his own education, that he doesn't really make the best "ordinary" example for his theory.)