I was privileged to hear an interesting dvar torah over Yom Tov on the meaning of "havdalah [separation]" in biblical Creation, and the application of this "havdalah" to marriage and divorce. One of the speaker's core ideas was that humans who wed become one, and should not, under normal circumstances, be divided.
Then today, in reading a presentation on Public Health planning, I came across the following Sufi saying:
You think that if you understand one, you understand two, because one and one are two. But you must also understand 'and'.
The point regarding Public Health planning related to the way that scale changes our treatment recommendations – we cannot recommend for millions what we would recommend for a single patient in a clinic. One patient plus one patient does not yield multiple patients with a multiple of the same recommendation.
However, I also see applications for marriage counseling. One and One make two, so I might assume that if I know the husband and I know the wife then I know the couple. But we must also understand the "and", the way in which they combine, in order to truly comprehend what this couple becomes when they are together.