Ashes of the parah adumah are used to make someone who has come in contact with a dead body tahor. Yet, these same ashes cause someone tahor who handles them to become tamei. Even Shlomo haMelech could not understand the paradoxical nature of this mitzvah. It is "chukas haTorah," a mystery.
Sefas Emes explains that death came into the world as a punishment for Adam's sin of eating of the eitz ha'adas, the tree of knowledge. The way to undo the taint of death that resulted from succumbing to the temptation for knowledge is to obey G-d even when his commands seem to defy reason and understanding. The most unfathomable chok is therefore the greatest metaheir.
I would put the idea this way: When a person relies on the eitz ha'da'as alone, on reason to the exclusion of all else, something within that person dies. Life can't be boiled down to equations alone, and to do so kills something of the human spirit. If one is willing to surrender and accept that there is more out there than our little mind's can fathom, that taint vanishes -- a person can live larger than the confines of his/her physical self and is not chained to the decomposing piece of flesh we all eventually become.