Luffy's -Zen: Beginner's Mind
1.) When they say Luffy is child like they don't mean literally. He's 18, he beats enemies to a pulp, declares war on the government, he's going to be fierce as Shanks and probably more fierce. He's been making progress at becoming pirate king.
What they actually mean when they say child like is not that he is some naive man child. What they mean by child like is that Luffy has a beginner's mind.
Shoshin (初心) is a concept in Zen Buddhism meaning "beginner's mind". It refers to having an attitude of openness, eagerness, and lack of preconceptions when studying a subject, even when studying at an advanced level, just as a beginner in that subject would. The term is especially used in the study of Zen Buddhism and Japanese martial arts.
The phrase is also used in the title of the book Zen Mind, Beginner's Mind by the Zen teacher Shunryu Suzuki, who says the following about the correct approach to Zen practice: "In the beginner's mind there are many possibilities, in the expert's mind there are few."
A related term, shōshin (正真), means correct truth and is used to denote a genuine signature on art works or to refer to any thing or person that is genuine.http://en.wikipedia.org/wiki/Shoshin
I knew about beginner's mind from one of my other geek/nerd areas that being survival studies. Beginner's mind is something that is essential for survival.