Choice, whether in the market of marriage or other goods, is always difficult. The information is always insufficient, the variables too complex. It is bad enough buying a new computer or television, when one often has to trust the salesman and a hunch – but if it goes wrong it is disposable. Choosing a partner for life is infinitely more complex and the guesswork involved is immense.
Some external force of desire is needed to help the individual to choose. Hence passionate 'love' overwhelms, justifies and provides an apparently external and compulsive authority. On the other hand, love within marriage is not necessarily as passionate or 'irrational'. It can be calm, calculating, very like any other 'work'. Yet if a decision is made to sever a relationship, the loss of that mysterious 'love' is often given as the justification.
Love thus seems to be at its most intense when uncertainty and risk are greatest, in that phase when humans have to choose. When they make the most momentous decision of their lives, which will turn a contractual, arbitrary, relationship into the deepest and most binding in life, love steps in as though from outside, blind and compelling. The heart has its reasons, even if the mind is perplexed.
So we might suggest that the pattern of romantic love, both before marriage and within marriage, is the result of a number of forces. The biological urge to mate, based on a deep attraction between males and females is universal. But the way in which cultures encourage, use, or discourage it varies enormously. In the majority of societies, the feelings have not been encouraged, marriage and love are not connected, and marriages have been arranged. This has made it possible to knit people together by family links.