AGI

OK, I am having one of those moments where I think I am going crazy.  I didn't know where to post this, so I selected this board. 

Section 1 taxes "taxable income."  Section 63 defines "taxable income" by reference to gross income in Section 61 minus deductions.  I know the deductions for AGI are not taxable, but I can't find that connection in the IRC.  Where does the definition of AGI in Section 62 fit into all this?  I know it is an above-the-line deduction, and I know this is very simple on the 1040, but where is the missing-link code section?  

Ever get any responses to this?