There is a familiar trajectory built into the way we talk about serious relationships. Two people meet, spend more time together, begin sharing routines, and gradually accumulate more of the infrastructure of life in common. Their friends overlap. Their holidays merge. They may move into the same home, combine finances, marry, raise children, and begin making major decisions as a unit. None of this is necessarily undesirable. For many couples, increasing integration is one of the great pleasures of love.
But there is an assumption hidden inside this progression that is rarely examined: Why should increasing love require increasing coupling?
In engineering and software design, two systems are said to be tightly coupled when each depends heavily on the internal workings of the other. A change to one component can require changes elsewhere, and the behavior of the whole system becomes harder to separate into independent parts. Tight coupling is not always bad. Sometimes it is efficient, elegant, or unavoidable. But engineers generally notice it because it creates dependencies, and dependencies affect how resilient a system is when something changes.
Loose coupling describes another arrangement. Two components can communicate constantly and perform important work together while still preserving substantial internal independence. Each system knows what it needs to know about the other, but neither has to reorganize its entire internal structure whenever the other changes.
