Do you think the lion, tin woodman and scarecrow were really without their brain, heart and courage?
The absence of heart, brain and courage is symbolic, not actual. In fact, the author wrote this book to see if he could attribute human qualities to non-human characters. So, for the Scarecrow to long for a brain, the Tin Man a heart and the Lion, courage is part of that overall plot. As these non-human characters try to discover their humanity, which the author suggests that they possessed all along, but just did not know how to access, Dorothy helps them as a force for good in the novel.
"The Scarecrow, Tin Woodman, and Cowardly Lion all seek external magic to give them qualities they already possess but fail to recognize."
The Scarecrow is already intelligent, he is the one among the group who figures out how to get out of bad situations, he is awarded a brain by the Wizard, but it is only an external symbol for what he already possesses.
The Tin Man is the most compassionate and caring member of the group, although he believes that he has no heart, he has all the characteristics of a person with a big heart full of love for others. When the Wizard gives him a symbolic heart, the Tin Man feels complete.
The Lion thinks that he has no courage, but courage is how you behave when there is something to fear. The Lion misunderstands what courage really is, the Wizard gives him a special potion that "transforms" the Lion, it too is symbolic.
Dorothy is a force for good in this story, and she opposes, and confronts evil, helping her three friends find happiness.
"The Wonderful Wizard of Oz contains numerous elements that open it up for interpretation. For example, the book has a dominant good versus evil theme, and it is presented in a straightforward manner that is easy for children to understand. From an adult’s point of view, however, the places and characters representing good (a child, the North, the South) and those representing evil (the East, the West) can be fitted into ideological categories."
The essence of The Wonderful Wizard of Oz lies in the basic understanding contained within "There's no place like home." The idea here is that one has happiness and only needs to realize it, revealed through experience and the reservoir of self sufficiency. This idea is critical in understanding the primary characters in the book. Each of Dorothy's colleagues already possess for what they are searching, just as Dorothy possesses happiness without having to leave home. The Lion does not need courage and strength, as he already is very strong and brave, demonstrated in his willingness to assume the responsibility for taking action when others won't. Acting despite fear is true courage, the Lion needs these experiences to demonstrate it to him. The Scarecrow does not need a brain, but actually proposes solutions and possible alternatives to the challenges the group faces. Intelligence is most present when one doubts, and whether it is through Descartes or the Scarecrow, this is why the Scarecrow begins to understand his notion of being smart. The Tinman already has a heart. His desire to want a heart, to want to love, represents this. His emotional compass is the most sensitive of the group members, and proves that the ability to feel pain and longing represent the highest caliber of emotional development for empathy is present. Interestingly enough, while all three possess their gifts, they need affirmation from an outside source, who does something cosmetic in order to affirm what he and all of us already know. The Lion has strength, yet only feels it when he drinks a concocted potion. The Scarecrow has a brain, yet only knows it when he accepts the makeshift brain of bran. The Tinman has a heart, but taking the symbolic silk heart allow him to fully believe in his own emotional identity. Confirmation in moments of doubt is needed for our true natures to be revealed.
I believe that all three characters, the Tin Woodman, the Scarecrow, and the Cowardly Lion, all had what they needed. They just didn’t realize it, because all three of them lacked self-confidence. Dorothy’s quest gave them the opportunity to band together for a common cause, to help her get back home; their own desires were secondary to their desire to assist Dorothy. Accomplishing their quest gave them the self-confidence they needed to claim their goals.
It may be interesting to look at the basic balance in each characters desire: Brain -> mental, Heart -> emotional, Courage -> physical, Home -> (you guess). One may have an ability, but may still require something seemingly powerless in order for the realization to take place. (ref: Dumbo's feather, Buddhist's "raft", Dorothy's Oz). It took the mental, physical and emotional aspects to be realized before Dorothy could go "home". Then again, maybe this is just pushing the box a little too much.