"Discontent, doubt and disquiet" was the way President Valery Giscard d'Estaing this week summed up the mood of the French as they set back to work after their traditional month off in August.

Giscard's detailed bread-and-butter attempt to dissipate that mood in a televised fireside chat was a lot different from his initial approach to the problem consisting of a lengthy interview in which the philosopher-president speculated, among other things, that maybe the real problem with the world is "the biological exhaustion of the species."

In any case, he said, it is a good thing that the consumer society is doomed by international economic conditions because it really was not suited to the genius of France.

"The sober society toward which we are heading is basically more adapted to France, a country of rural origins that preserves its attachment to the land and has a sense of time and measure," he said.

The satirical weekly Canard Enchaine wrote ironically about the president "comfortably seated up there on his little cloud" and noted that "when Giscard ventures into general ideas and vast historico-philosophical panoramas, one is struck by the banality of his words and the platitude of his thought."

Giscard's Olympian approach -- letting his prime minister, Raymond Barre, act as a lightning rod for the general discontent -- has not been going over with the general populace, either. A poll for the conservative newspaper Le Figaro showed Giscard's popularity had slipped from 54 percent in July to 49 percent in September, while Barre slipped from 36 percent approval to 29.

Until that poll, it had been an article of faith among French political analysts that Barre's unpopularity would only serve to reinforce Giscard's determination to keep him on the job as a shield to deflect dissatisfaction from the president. The poll demonstrated that Barre's unpopular economic measures were beginning to hurt the president's image as well. The only consolation was that the media kept comparing Giscard's 49 percent (down from 62 percent in January) to President Carter's 19 percent.

So, Giscard who in the past has vaunted Barre as "France's best economist" and as "the Joffre of economic recovery" -- a reference to Marshal Joffre, who saved Paris from the advancing Germans in 1914 at the first battle of the Marne -- was reduced this week to praising his prime minister for his honesty "above all suspicion," for his lack of "any personal ambition as far as I know" and for the respect he gets from foreign leaders.

AS THE FRENCH were loading up their cars for the annual August exodus, Barre announced a breathtaking series of raises in prices charged by state-controlled companies for such goods as cigarettes and gasoline and in the rates of the state electric, gas, railroad and urban transport services.

Giscard conceded that those raises were responsible for half a percentage point rise in the cost of living, without counting the enormous new bite in paychecks for additional social security withholding. It has been a standard tactic for the government to wait for people to go on vacation to announce such measures, and French governments always have managed to minimize the grumbling that way. This year it didn't work.

Communist Party leader Georges Marchais had taken his vacation in July and publicly announced that he intended to take advantage of everyone else's being off on vacation in August to get a lot of exclusive media attention. But there was such an outburst of public indignation over Barre's measures that Marchais' voice was almost drowned out by other political leaders issuing statements from their country houses. One of the state television networks wound up devoting an hour a day to interviews with political leaders, mostly on beaches or docks.

As if the reality did not suffice for the summer of France's discontent, there were other small economic humilations full of symbolic affronts to French national pride.

It was bad enough that the liner France, former luxury flagship of the French line, had been on the auction block for several years. But its new Norwegian owner, who rechristened it the Norway, spirited the vessel out of its home port of Le Havre despite the loud protests and demonstrations of the Communist-led shipyard workers. The workers insisted that at least the huge contract for refitting and overhauling the ship should have been kept at home. But a West German shipyard came in with a bid of $52 million and promised to do the work in 10 weeks' less time than the French, who bid 85 million.

THEN, WORD CAME that barring a miracle, the Casino de Paris -- legendary showcase of Mistinguett, Maurice Chevalier, Josephine Baker and Line Renaud -- would have to close its doors in November at the end of its current production.

This was followed by a preliminary deal to transfer from Lebanese owners to still other foreign hands -- this time to the English, of all people -- the hotel group that includes the world's best-known sidewalk cafe, the Cafe de la Paix, and the hotels Meurice and Prince de Galles. It served to rub in the awareness that practically all the great palace hotels of Paris have had to be sold to foreigners in the past few years.

YET GOVERNMENT strategists express confidence that they can weather any challenges because the various elements of opposition are so divided against each other. The unions cannot seem to get together for a united protest. The Communists and Socialists still spend at least as much energy sniping at each other as at the government, and the Socialist Party has never seemed so faction-ridden.

The Gaullists are in such disarray that they are very seriously thinking of setting party leader Jacques Chirac aside and running their leading old warhorse, Michel Debre, 67, Charles de Gaulle's first prime minister, as their presidential candidate against Giscard in 1981.

"We wish there were someone out there standing up so that we could attack him," said a Giscard intimate."But every time we lash out, we can't find anybody there to hit. There is one real force there -- the electorate, and it's clearly unhappy. We may not be entirely safe from a spontaneous outburst of public madness like in May 1968. But we think we can count on the Communists to preserve us from that. They've learned a lot since then, and they won't let themselves be outflanked by extreme leftists again."

Meanwhile, Giscard often seems to be lost in reverie about the future of the human race and to oscillate between profound pessimism and, when that is challenged, a decidedly unenthusiastic optimism.

Soon after the end of vacation, he said, "We are moving toward an uncontrolled world . . . . You asked me whether I have perceived the flickering of a new civilizing idea. The answer is no."