What a strange nuclear place Ronald Reagan has brought himself and the rest of us to. Just a few years ago the air was thick with denunciations of him as a nuclear cowboy, the mad bomber of the West, the relentless nuclear armer. The nuclear freeze movement sprouted, the peace movement thrived.

Now he has in his hand one arms control agreement, has in his sights a second much larger agreement, and is being denounced in formerly friendly quarters for a readiness to pronounce nuclear deterrence evil and to accept nuclear disarmament as a worthy goal. The freeze and peace movements have been rendered marginal.

The earlier Reagan was never as monstrous as people said. He came to be seen in nuclear matters as casual verging on careless, untutored even when inadvertently sensible, insensitive to the anxieties he aroused on several continents. His image sometimes victimized him: when he suggested in 1981 that a limited nuclear war might not escalate, the European journalists interviewing him presented this innocent observation as a confession that America would fiddle while Europe burned. He seemed convinced that the Kremlin had lost respect for American will, that deterrence as a nuclear strategy was dangerously flabby and that it was necessary to go over to the risks and rigors of ''war-fighting.''

But Reagan did not do crazy things and, with one exception, did not make major innovations in nuclear hardware or doctrine that were without roots in ostensibly more moderate administrations. So it looks to many of those he formerly drove up the wall, anyway. He did not get into any crisis with the aspect of a potential nuclear confrontation.

His erstwhile critics find it tempting now to attribute the president's passages of success or effectiveness to his luck in facing three geriatric cases and then the new-thinking Mikhail Gorbachev in the Kremlin. Actually, we may need a longer view to determine whether it was luck or was in part the credibility that accrued to him by virtue of his political style, his rearming program or even his maverick's reputation.

Reagan's major innovation was the Strategic Defense Initiative, an example of new thinking that Gorbachev, for one, still is not ready for, at least in Reagan's much-advertised foot-to-the-floor version. Nor are many others. But SDI sharpened the Kremlin's appetite for negotiation, and may yet help produce agreement -- agreement that SDI doubters cheer -- on dimensions surpassing their boldest aspirations.

Or there may be no such agreement, although my sense of it is that either in this administration or the next a way can be found both to reduce offensive arms and to keep work going on defense within shared bounds. Even if this does not happen on Reagan's watch, it will be the fruit of his policy -- that is, of his extremism or vision, whatever you call it. No pain, no gain.

Experimentally, Reagan and Gorbachev have moved a small, comforting distance toward demonstrating that humans can control their nuclear destiny. Joint regulation of the size and shape of armories isn't everything. Each side's political and military care in handling nuclear arms in a crisis is more crucial to averting war. Still, the spectacle of politicians' inability to limit the producing of weapons of global destruction is plenty scary -- scarier, because it is presumably easier but yet has not been done, than the thought of losing control in a crisis. It's not that the weapons, lying around or even being aimed, are dangerous in themselves, although they are dangerous. It's the syndrome of the sorcerer's apprentice: governments ever more frantically performing a mad task that has gotten entirely out of hand.

Reagan cherishes a very personal vision of a nuclear-free world, a thoroughly safe, thoroughly inspected place protected everywhere by a made-in America defensive shield. Many others, however, will be satisfied with a less perfect world and will prefer to hold on to enough offensive weapons to sober the other big players and to guard against wayward small crazies. Enough nukes might remain deployed here and there to destroy the planet, but people would be living with the bomb. ''Numbed?,'' as the peace movement has it? What about respectful and alert?