This idea of twoness above is not as vague as it sounds, for we can agree on a certain arbitrary model set containing what we call two things, our cow and rock if we wish, got by counting or other means, and declare that any other set has two things if it can be put in one - to - one correspondence (in modern terminology, bijective correspondence) with our model set. (religion-online.org)
Matrimony reminds us of the earthiness of human clay, breathed upon by God's love, and of the completed, united twoness of our essential nature. (firstthings.com)
Jesus extrapolated a limitation of two persons in a sexual union (serially or concurrently) from the foundational twoness of the sexes established at creation (Mark 10:6 - 9). (firstthings.com)