Years ago, Rabbi Aryeh Kaplan z''l wrote a small booklet entitled Waters of Eden outlining the basic laws and some of his philosophical musings on the Mikveh, the Jewish ritual bath. In that rich pamphlet, he noted some powerful and beautiful ideas about the concept of Mikveh.
First, he focused on a common Chasidic conception of the Tree of Knowledge of Good and Evil, promulgated by the Baal Shem Tov and many others. Originally (presumably in an ontological and not necessarily temporal sense), humans were purely good, with evil manifest externally. Enter the slithering snake as sinister symbol. After consumption of the fruit from the tree, however, good and evil were then (and now) bound together. More than the metaphor of entangled cords, it seems more proper to analogize by assigning to evil the role of soluble dissolved in a solvent; think sugar in tea. On Shabbat, to emphasize the point, I mentioned a profound interpretation of the Gaon Rabbi Elijah of Vilna. A famous verse in Ecclesiastes states, "For there is not a righteous person on Earth who does good and sins not." (Ecclesiastes 7:20). The common understanding is that no one is perfect; all people sin. Taking a more literal interpretation, the Gaon explained instead that every good deed is inherently mixed with some element of sin, be it improper motivation, ego, gain, etc. Anyone who performs a good action will also sin in some sense; it's simply the cost of doing business in our post-Edenic world.
Central to Rabbi Kaplan's thesis (it made the title!), he focused on the verse, "[a] river went out of Eden to water the Gaden, and from there it separated and became four headwaters." (Genesis 2:10) The Talmud in Berachot (55a) notes that all of the world's bodies of water are sourced in the original river leaving Eden. Immersion in the Mikveh, and purity in general, is an attempt to return to the well-intentioned world of Eden where human desires are pure and plain. Halachah requires absolutely immersion in a natural body of water to achieve taharah, purity. Personally, I understand this to mean a mode of operation where we strongly and innately desire to act righteously and put our best foot forward. This is something we all feel on occasion, and try to make our common mode.
How sadly ironic that the mikveh itself has now become the model of the blurring between the pure and the profane, and that the natural source of our return to honesty, humility, and trust in humanity's best intentions has transformed into a vestige of that very real and perverse world in which we live. Is it possible to find purity in our world?