Women just don't make sense, at least some of the time. For example, my wife Lynn gets angry with me (on a very rare occasion). That's not the part that doesn't make sense - I do plenty of things to make her angry. What doesn't make sense is when she won't tell me why she's angry - even when I ask. Sometimes when I ask what's wrong, I get "if you don't know already, then I'm not going to tell you". Men, look close - this is woman at her most irrational state.
I don't know. If I did, I wouldn't have asked. Her mind and emotional states are so complex, I often have no hope of navigating the raging waters safely! She is, at times, beyond my ability, as a guy, to comprehend.
When I read Romans 11:33-36 I get the same feeling (not the frustration, but the sense of awe and mystery). "Who has known the mind of the Lord" Paul asks. No one. It is unfathomable. He knows himself fully well, and that right there is enough to say that I can't fully know his mind - it comprehends the infinite, I never will be able to do that. It is complex and deep ("Oh the depths!").
This reminds me that reason alone is never enough to bring me to a deep or saving knowledge of God. We need his self-revelation to us. We need a "divine and supernatural light immediately imparted to the soul" (Edwards).
Even then, we must acknowledge that God will always know things that we do not. Spurgeon counseled a young divinity student saying, "We must allow God to know things that we do not".
Paul was writing in Romans 8-11 about the sovereignty of God in the salvation of men and women (predesitination and election) and he concludes this section with a doxology reminding us that God's ways are beyond tracing out. Amen Paul, Amen.
PS. Lest Lynn get angry with me and so I don't have to guess why, lets keep this conversation between us!