Tim Geithner is not a creature of Wall Street.

This assertion may seem shocking and wrong to the many, many people for whom Mr. Geithner is the human symbol of the Obama administration’s undue deference to the financial institutions that caused a near-collapse in the global economy. Mr. Geithner was an engineer of the bailouts; an opponent of nationalizing banks; a minimally enthusiastic supporter of programs to help homeowners directly. With his spread collars and tailored suits, he even looks like a Wall Street sharpie.

But Mr. Geithner spent his youth largely abroad and his early adulthood working on international trade and economics in the United States Treasury Department. Only starting in 2003 did he have much of anything to do with the financial industry, and that was as its overseer at the helm of the Federal Reserve Bank of New York. He is now the president of Warburg Pincus, a private equity firm, but he has held that job for all of 10 weeks. He was never an investment banker like his predecessors Hank Paulson and Robert Rubin, or even a hedge fund consultant like Larry Summers.

As far back as college, as he puts it in his new memoir, “I had never thought of finance as a particularly special or prestigious profession.”

All of which makes the fact that he earned a reputation as a tool of big financial interests that much more intriguing. After covering Mr. Geithner for the better part of a decade and reading the memoir, I think here’s the best way to make sense of him: Timothy Geithner isn’t captured by Wall Street. He’s captured by working within systems as they exist.