I RETURN to Manhattan, Kan., and the fall of 1970 to cite an incident that took place at a Kansas State University fraternity, a verein of vacuums I belonged to briefly in a vain effort to become more impressive to the campus' miniskirted cuties.

Nine years ago at Kansas State, pot still wasn't the omnipresent force it was at such vaunt-couriers of enlightenment as Colorado College, the University of Miami and Yale. But even at K-State the tide was sweeping in faster and faster, and among the denim-clad, bell-bottomed apostles of hip, pot was as fashionable as tuxedos and grammer were passe.

The highest priest of pot consciousness, perhaps in the whole state of Kansas, happened to be my roommate and he spent a good part of the fall semester trying to convert me to the rites and arcana. He touted pot as the key to a refined appreciation of sex, poster art, Charles Reich and Carlos Castaneda. Beer brings only hangovers, too many trips to the restroom and flab.

I wish I could claim credit for the incident I now recount, but credit goes to Jeff Jernigan, a shrewd cynic who, last I heard, was working in a bank in Topeka. One evening Jeff walked into the room and offered my roommate a pipe in which, he assured him, was some "incredible pot, dynamite stuff." My roommate took a toke and went into the postures and hipspeak appropriate to being stoned. The stuff, it appeared, was indeed dynamite. Each toke was the full equal of week of nude sensitivity training and 100 pages of the philosophy of John Lennon.

Then Jeff revealed that the stuff was mere pipe tobacco, not pot. Now, I savored some cruel pleasures in my wasted youth; I sprayed cold water on the faces of people in lower bunks from a hose strung through top bunks; I walked out in the middle of Elliot Gould movies and episodes of "Star Trek." But all I can say is that you had to be in that room, not just to see, but to feel the enormity of the mortification of my roommate as the fool's cap descended over his brow.

"Yeah . . . Well, I always did say it was 50 percent phychological," he gulped.

I suspect it's more like 90 percent. This suspician was reinforced a year or so ago when I read an account of a study in which one group of people was given a neutral substance and another group a sizable injection of THC, the active agent in marijuana. No one was told who was getting what. No difference was found in the reactions of the two groups.

I do not wish to quarrel with research findings about serious physiological effects from pot. I just call attention to the power that suggestion plays in getting stoned. To a smaller degree, the same may apply to booze, at least judging by the teetotalers who often act as crazy as the worst toper on New Year's Eve.

But the parellel goes only so far. For one thing, the effects of booze have been much more widely and objectively documented. For another thing, few drinks to get drunk, even if they too often end up drunk. But who smokes pot except to get the so-called high? The innumerable forms the "high" is said to take -- relaxation, "deeper sensory awareness," sexual arousal, etc. -- further indicate that it is everything and nothing.

Whether or not pot is psychologically addicting, the point is that the potheads I've known were all blanks long before they took to pot. For them, pot merely made vapidity hip. It became not only acceptable but actually desirable to do nothing but smoke, giggle and like Led Zeppelin. This is not addiction to mindlessness, or even a rationalization of it; this is nothing short of an exaltation of it.

In the November 1978 issue of Psychology Today, Washington internist Michael Halberstam cites a few of the things that he believes account -- or at least used to account -- for the pleasures of pot smoking. Usually it amounts to, "Look at me being sophisticated enough to do what dullards can't appreciate. I'm cool enough to do what the uptight establishment thinks is naughty."

As Halberstam remarks, with the fading of the counterculture pot lost its value as a symbol that one was in the vanguard of the revolution, that the times weren't passing one by. In Washington today, says Halberstam, pot users tend to be the sort of compelling personalities who jam into Ted Nugent concerts -- "the losers," he concludes.

This may indicate that at this stage legalizing pot would not greatly increase its use. Teenage use rose greatly over the last decade, and with legalization it would doubtless rise some more, but I doubt that the increase would be even remotely as great as the increase in drinking that followed the repeal of Prohibition. The reason, as I have indicated, is that a good deal of pot smoking does stem from the forbidden-fruit appeal. It demands only a tolerence for extended staring into space, and it offers the thrill of feeling naughty, a thrill that once was coupled with the security of feeling hip.

Pot, then, once turned deficiencies into marks of fashion. But what about now? What of the counterculture revolution, of the greening of America, of peace and love, of poverty and ugliness for their own sakes? Pot was part of it all, but was it all for naught? Not quite, Pot's made mindlessness fashionable, and is not mindlessness alive and kicking? It rides high in the discos, for example, whose music drowns out conversation far better than a mere television set can.

So, in their own modest way, potheads did make what, loosely speaking, might be called a revolution. Some of them gave their all to green their little patch of America. It was a bit different from the revolutions of Washington and Lenin, to be sure, but one whose stalwarts, I believe, would have been willing to forge on had their parents been willing to keep paying for it.

Alas, they weren't, and the torches had to pass to the teen-agers, who couldn't seem to grasp what pot had to do with art or politics or consciousness. But once there those who did reach out for such an understanding, and they should not be forgotten.