Dylan's "Blowin' in the Wind" asks a series of rhetorical questions, some gentle, some searing. Rhetorical questions are questions for which the answer is obvious or already known. They are meant to make us think.
Dylan begins each stanza with a question that is more abstract than emotionally laden, such as "How many roads must a man walk down" before he knows he's a man? That is an important question to ponder, but it does not hit us in the gut.
Dylan will ask a question (or two) like the one above and then hit the reader/listener with a more gut-wrenching query: in the first stanza, it is
Yes, 'n' how many times must the cannon balls fly
Before they're forever banned
Wow, how did we get from maturity to war?
Dylan then brings in his refrain: that the answer is blowing in the wind. This refrain is ambiguous, meaning it can be interpreted in different ways, but one interpretation is that we already know the answer: it is out there, all around us, accessible, blowing in the wind. In the case of the cannon balls, for example, the obvious answer is that we know it is long past time for them to be banned--and if we do not, the song invites us to think about this.
The same technique repeats throughout. In the second stanza, Dylan again begins with a gentle and generalized question about how long the mountains can last, then moves to more pointed question: "How long can people live without being free?" and then moves into the gut punch:
Yes, 'n' how many times can a man turn his head
And pretend that he just doesn't see
Again, the answer is blowing in the wind: we have already turned our heads away too many times; this is a statement all the more intense for people in the early 1960's, for whom the Holocaust was a living memory, and the civil rights movement a living reality.
The third (and final stanza I will discuss) repeats the same device of escalating the emotional heat of the rhetorical questions, the final one a gut wrencher:
Yes, 'n' how many deaths will it take till he knows
That too many people have died.
This poem/song aims squarely at our emotions in order to sensitize our consciences. Dylan's point is that enough evil has already occurred in the world for us to say "Let's stop." Enough. The language is simple and direct and for that reason, all the more powerful. It has a biblical quality: Jesus, for example, used rhetorical statements to awaken people, telling them if they had ears, then to hear and if eyes, then to see, as Dylan does when he asks:
How many ears must one man have
Before he can hear people cry
While we have to take any poet's interpretation of his work with a grain of salt (once a poem or work of art is released into the world, the artist no longer owns or controls its interpretation), Dylan has commented on this famous work, and his response points to the idea that many problems have simple solutions that do not require a roomful of experts to solve. The answers are accessible to anyone:
There ain’t too much I can say about this song except that the answer is blowing in the wind. It ain’t in no book or movie or TV show or discussion group. Man, it’s in the wind – and it’s blowing in the wind. …But the only trouble is that no one picks up the answer when it comes down so not too many people get to see and know . . . and then it flies away. I still say that some of the biggest criminals are those that turn their heads away when they see wrong and know it’s wrong. I’m only 21 years old and I know that there’s been too many . . . You people over 21, you’re older and smarter.