Why did he need the doctor if he did not trust him?
Sure he healed his hand, treated his son, but why did he need Garrigan in particular?
Amin at one point tells him that he is nothing. Amin also says that he cannot trust anyone yet that is not completely true. A close individual who is suspicious of Garrigan at the end tests his pills on a child. Clearly this man is loyal and more trustworthy.
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Use the Force.