PARIS -- If you are concerned about nuclear-arms control, the ''zero option'' and all the rest, come to the City of Light. Everything will fall into place in all of its characteristically French complexity.

At first glance, it seems simple enough. In April Mikhail Gorbachev pulled from the wreckage of Reykjavik the one arms-control offer the United States and its Atlantic partners couldn't refuse: the so-called ''zero option'' to remove Intermediate-range Nuclear Forces (INF) on both sides in Europe. He was, after all, accepting what had been a European offer in the first place.

To begin at the beginning: In 1979, the North Atlantic Treaty Organization had built the ''zero option'' into what was called the ''two-track'' strategy for countering a massive Soviet INF arsenal of SS-20s. The idea was that the Europeans would agree to a buildup of a matching ''INF'' force of U.S. Pershing II and cruise missiles unless the Soviets would negotiate a balance of this category of nuclear weapons at lower levels, not excluding none at all.

Ronald Reagan explicitly endorsed a European ''zero option'' in his first year as president. But the negotiating ''track'' went nowhere. So the offsetting force of American-supplied Pershing and cruise missiles was deployed.

It was (or so it was argued) a classic case of the arm-to-parley theory of disarmament. We armed and they parleyed with Gorbachev's offer to come down to zero. For the allies not to agree would have made them appear, as one French policy-maker puts it, to be ''weapons crazed.''

Then Gorbachev's plot began to thicken. In an act of what seemed to be selfless generosity, he added an offer to remove a category of shorter-range INF (now known as SRINF) of which the Soviets have a sizable number and the alliance has none. So what was first thought of as simply an INF trade got more complicated. INF was split up between longer-range intermediate-range nuclear forces (LRINF) to distinguish them from SRINF. Thus we were introduced to the ''double zero option.''

If you are the least way confused, the French are well-positioned to straighten out your thinking. Half-in and half-out of NATO, the French take a certain distance from alliance business. They are (like Britain) an independent nuclear power in their own right. But geography as well as history would be reason enough for them to take an intense interest in European, and particularly West German, security.

It is fair to say that there is a basic consensus among French political leaders that the Soviets have zeroed in on Europe, so to speak, because ''de-nuclearization'' of Europe is for now their first priority.

A ''double-zero option'' for Europe, it is pretty much agreed here, would set a pattern that would inevitably turn attention next to even shorter-range nuclear weapons and raise the awful specter of a nuclear war fought exclusively in West (and East) Germany.

The pressure from the Germans, not to mention the Soviets, for sweeping Europe clean of nuclear weapons of all categories -- including not only ''battlefield'' arms but the French and British independent forces -- might then become nearly irresistible. Ultimately the European allies could find themselves up against what one French official calls a ''crushing'' Soviet advantage in conventional and chemical weapons.

The whole strategy of nuclear deterrence, which works only so long as the threat of a nuclear exchange remains credible, would then go by the boards. Small wonder that many French and other European strategists wish the word ''zero'' had never gotten into the vocabulary of nuclear-arms control.

The point is not whether Gorbachev is actually bent on ''crushing'' Western Europe. It lies in the danger of a gradual demoralization of the European public. If ''zero-ism'' becomes a pattern, European strategists fear that the dismantling of whole categories of nuclear weapons could be perceived as a ''decoupling'' from the deterrent effect of American nuclear power.

''We have to break out of the Soviet logic,'' says one high-ranking French official. By this he means that the allies must somehow join in resisting the ''logic'' of carrying superficially appealing ''zero options'' to the point at which the deterrent effect of the threat of nuclear war loses the power to deter.