I’m sorry but nine years is not impressive to me. (Although a lot of people here will no doubt try to support the “impressiveness” of the “feat” by noting his age. But age is irrelevant to those who use mnemonics.)
Figure it this way: with mnemonics, you ought to be easily able to memorize one of Shakespeare’s sonnets every day. And that’s a minimum! Since there are ONLY 14 lines, it should take you no longer than 1 hour (at the most!). You can see how easy it would be to memorize MORE than one a day.
If you divide 10,565 (the lines in Paradise Lost) by 14 (the lines in a sonnet), you’ll see that there are approximately 755 “sonnets” strung together. Now, having learned a mnemonic system means that you know that learning the lines of a poem doesn’t depend on the “type” of poem it is, sonnet or blank verse, haiku or epic. Memorizing words doesn’t depend on the material, it depends on the system you use.
Now then, if you divide 755 (sonnets) by 365 (days), you get about 2 sonnets (28 lines) per day (round it off to 29 lines). This means that in order to memorize Paradise Lost in ONE YEAR, all you have to do is memorize the equivalent of about 2 sonnets per day (29 lines per day x 365 = 10,585). Imagine what would happen if you memorized THREE sonnets in one day!
To put it another way, if you divide 10,565 lines by 365 you get 28.9 (round it off to 29), which is approximately the sum of 14 + 14, or 2 sonnets per day. Think about that: say it takes you one hour to memorize a sonnet. All you have to do is set aside 2 hours per day (they don’t have to be consecutive hours) for a year and you’ll have Paradise Lost firmly in your memory in ONE YEAR.
And setting aside only 1 “sonnet” per day (14/15 lines at 1 hour per day) and memorizing it in 2 years, is still, to my mind, a good job! In other words, if you can memorize 1 sonnet per day (how could you not?), then you can memorize Paradise Lost in 2 years!
Nine years? He must have been using a rote system, not mnemonics.