At an ultimate level, opposition in all things can be taken as a phrase describing the fundamental metaphysical principle that creativity (taken here to be identical with progression in the harmony with God’s creation) must be a product of two distinct and in-a-sense ‘opposed’ principles.
As the ultimate creative act of having a child comes from the interaction of two persons of the two sexes, so spiritual progression comes from the interaction of ‘opposites’; and what these and other creative situations have in common is that there is a ‘polarity’ (to use Coleridge’s term) in which the two sides are distinguishable but not divisible.
There are many similarities between men and women; but there is also a complementarity of nature which goes beyond the specifics of parturition – the feminine has always been recognised as a ‘centripetal’, gathering, unifying principle; and the masculine as a ‘centrifugal’, exploratory and differentiating principle – both of which are required to make that ‘vortex’ of new life and potential that is a child.
At its very deepest possible level of analysis; life (and love, as its basis) is dynamic, active, creative – and this is because fundamental reality is always a polarity.
(Note: This insight came to me yesterday when reading, and for the first time understanding, the final – and most difficult – chapter of William Arkle’s A Geography of Consciousness, 1974.)