@EvoWarrior5:
I've debated the Zoro voice issue here once before, but I never really arrived at a satisfactory conclusion, and whenever I thought about it recently I resolved to just give up on trying to figure it out. This, however, is definitely the best description I have seen matching that scene to a setup for Haki. Thank you.
Can't agree with Greg on this point. I'm gonna go ahead and say that he used CoO to dodge the falling rubble, but CoA to cut steel. I'm gonna write my interpretation on haki so bear with me:
Haki is pretty much anything related to willpower (duh).
CoO is the ability to sense the will of other people. Since all people have haki to some degree, it allows you to sense pretty much anyone, including objects. The more "will", or "intent", someone or something has, the easier it is to sense them. It could be someone extremely happy, or an arrow sent with the intent to kill. I think that when Fujitora was listening to the citizens of Dressrosa, he wasn't hearing them verbally, but rather their joy and determination to get in his way, along with Fuji's expertise in Kenbunshoku, were strong enough for him to accurately discern what they were talking about.
During the adventures of the strawhats, we've seen them learning to dodge and parry better and better, to the point where Zoro could dodge a bullet from almost point blank range in Shabondy.
This is where the VoAT comes in. The more a subject is detached from what a person can physically understand, the harder it is to understand its will, but if your CoO is powerful and unique enough, you can understand the will (or voice) of anything. That's why Roger could understand the poneglyphs- they were carrying the will of those who wrote them, and Roger was listening to it. That's why Luffy and Roger could hear the Sea Kings while others couldn't- it's just too difficult to physically communicate with them (even fishmen can't), so you'd need an incredible haki to hear them. When you're very close to something it will be easier for you to hear its voice, like with Merry. That's what makes it so interesting to me, because there's no character in the entire series who's more sensitive to other people's wills than Luffy. The latest example would be just last chapter where Luffy made Momo express his will to defeat Kaido, which leads us to the next part.
If CoO is the ability to sense the will of others, then CoA is the power to express your own will.
I think that saying that CoA is just about hardening would be a complete underestimation of the entire concept of haki. CoA can be anything from striking harder at your opponent or blocking an attack, to standing up despite all odds (Luffy standing up before his final attack against Lucci) or cutting things that no amount of physical power or technique would allow you to cut with just a sword (cutting steel, and Kinemon cutting fire).
The important thing is, that on all occasions you express your will to make something happen: to defeat an opponent, to not yield to an attack, to not let that guy go after my friends. It's pretty much systematizing the "power of friendship" with a bigger scope.
That's why I take this line by Nami quite literally:
! 
No, not without limit, but their spirit was weakened in Water7, and they certainly gained a haki boost when they went to EL.
When you keep overcoming obstacles, your willpower becomes stronger and it becomes easier for you to express it and make things happen your way. There are two interesting lines regarding this point: one by Zoro, saying that everyone were continually becoming stronger with each adventure, and BB noting that Luffy's haki is stronger than what he remembered when Luffy punched him (I'm sure you remember those lines, I don't feel like scooping the series for these pages).
Anyway, when you use busoshoku, your will needs a target, as I demonstrated above. This can be especially seen when Zoro uses haki when he declares his will to cut everything in his way. That's why I think Zoro used busoshoku when cutting Daz. His will was to cut steel- and only steel. Nothing else. That's why his blades wouldn't cut the leaves, and his willpower was strong enough to turn his will into reality. The more willpower you have, and the better you use it, you can use it to accomplish grander feats, such as cutting fire. On the other side you the basic feat of being able to touch a logia.
I'm guessing you already thought about most of these things, but I wanted to give another PoV at this since the subject was brought up.
