what does the author (Mario Puzo) mean by the following sentence?

Question

What does the author (Mario Puzo) mean by the following sentence from The Godfather?

There was no greater natural advantage in life than having an enemy overestimate your faults unless it was to have a friend underestimate your virtues.

It comes from the following passage:

The Don considered a use of threats the most foolish kind of exposure; the unleashing of anger without forethought as the most dangerous indulgence. No one had ever heard the Don utter a naked threat, no one had ever seen him in an uncontrollable rage. It was unthinkable. And so he tried to teach Sonny his own disciplines. He claimed that there was no greater natural advantage in life than having an enemy overestimate your faults, unless it was to have a friend underestimate your virtues.

Answer 1

The Don is saying that if an enemy thinks you are less capable than you are, by thinking your faults are larger than they actually are, it is a great advantage. He also says that if a friend thinks you less able or less good than you are, this is also an advantage. He uses a parallel construction to express these two thoughts. The parallel construction contrasts "enemy" with "friend", "faults" with "virtues", and "overestimate" with "underestimate".

In fact he is saying that having both friends and enemies think less of you then is accurate, although in different ways, is a good thing. Exactly which faults and which virtues the Don refers to is not stated, so it suggests all possible faults and virtues in general.

That the sentence starts with "He claimed" indicates that the narrator does not endorse this idea, and perhaps implies that it is not true.

Answer 2

David Siegel's answer is good but I disagree with his interpretation of "unless" and what meaning it conveys.

The generalized sentence structure here is:

There is no better [descriptor] than [awesome thing], unless [even more awesome thing].

You might wonder why the speaker would even bother mentioning [awesome thing], only to immediately override it by mentioning [even more awesome thing]. There's a few possibilities here:

• Maybe the speaker forgot about [even more awesome thing] and remembered midway through speaking, therefore amending his sentence.
• The speaker may have assumed that [even more awesome thing] wasn't available or a long shot, and therefore mentioned something more feasible as a fallback option.
  • This doesn't quite apply to your case. But it is a possible explanation, e.g. "I'd love to have a cup of tea, unless you still happen to have some of that rare scotch?"
• The speaker may have intended to mention both things and rank them, and they chose this phrasing because it mentions the second best thing before the best thing
  • Compare this to "scotch is better than tea". Comparatives tend to introduce the best thing first.
  • You could say "tea is worse than scotch" so you keep the best thing for last, but then you are implying a negative connotation, and in your example the speaker clearly intended to speak highly positively about both things.

So when you commented the following:

I'm wondering if he also meant your friends underestimating your virtues is a greater advantage than your enemy overestimating your faults.

You are exactly right. The phrase expresses that both are great advantages, but then goes on to point out that friends underestimating your virtues is even bigger of an advantage.