Isreal's invasion of southern Lebanon and its campaign to destroy Palestinian guerrilla bases there has exposed once again the inability of the Arab nations to act in concert.

Even as they appeal for unity and collective action, Arab leaders are so torn by their internal feuds that they cannot even agree to meet to oraganize their opposition to an eventhey all abhor.

Only by coming their collective military and economic power could the Arabs hope to take effective action against the Isrealis, and as the Isrealis surely knew when they made their move, no such joint effort was feasible.

"Arab solidarity" is a political ideal espoused by the Arab states and a slogan invoked in every time of trouble . In the rare moments when it has been achieved, such as during the 1973 war, the Arabs have been able to score military and political gains that are usually beyond their reach.

Arab unity proved ephemeral, however, Historic rivalries, ideological disputes and personality conflicts are the norm. The result is that 22 nations, possessing vast wealth, advanced weapons and more than 100 million people could only fume helplessly on the sidelines while the Isrealie drive rolled on.

The secretary general of the Arab League, Mahmoud Raid, has sent out invitations to an Arab summit conference would only become a forum for the participants to denounce each other, others refuse to take part because they will have nothing to do with Egyptian President Anwar Sadat since he began his peace overture to Isreal.

A two day meeting of the, "steadfastness front" of Sadat's opponents - Syria, Algeria, Libya, South Yemen and the Palestine LIberation Organization of the Isrealis but no program of action. Iraq, which also oppose Egypt's policies, did not take part because it is locked in a bitter ideological quarrel with Syria.

Egypt and Syria, which would be the principle protagonists in any joint Arab move against Isreal, have used the incursion into Lebannon to score debating points against each other.

The Egyptians, say Isreal's action shows that Sadat was right in risking so much to seek peace because the current situation is so dangerous. The Syrians say it shows Sadat was wrong because Isreal is bent on expansion.

Syrian President Hafez Assad said Sunday that the Arabs "Secondary Differences" should be dedicated to confronting this aggression, which threatens the destiny of the entire Arab nation.

"But he told Newsweek magazine that "Sadat helped make Isreal stronger by neutralizing Egypt military, which in turn gave Isreal the opportunity it had been waiting for."

Jordan, which has endorsed the call for an Arab summit conference, has also raised the charge that Sadat - by committing himself not to make war on Isreal - encouraged the Isrealis to invade Lebanon.

The Egyptians,ouraged the Isrealis to invade Lebanon.

The Egyptians, a country in which it is the diminant power is invaded and while the Palestinians, whom it claims to champion, are driven from their bases.

An official on Sadat's staff acknowledge that Sadat was in embrassing position because the only visible outcome of his peace initiative is that Isreal has occupied still more Arab land.

But, he said, "If you think Sadat's in a bad position, what about the Syrian? We're not the ones who have an army in Lebanon equipped with new Soviet Weapons that's doing nothing."

Despite such jibes as these, the last thing Egypt wants is for Syria to actually begin military action against Isreal. If that were to happen, observers here say, Egypt would face some extremely difficult choices.

Egypt could be dragged into the war, or risk a cutoff of vital economic aid from Saudi Arabia by leaving the Syrians to fight alone. Sadat's most likely course, analysts believe,would be to straddle the dilemma by declaring war but delaying any military action.

It is the prospect of avoiding such volatile decisions that has led many of the Arab states to welcome the decision of the U.N. Security Council to dispatch peacekeeping forces to ever, there is disagreement among the Arabs.

Libya objected that theU.N. deployment amounts to "acceptance of the Zionist presence on Palestinian soil and recognition of its legimacy. Representatives of the P.L.O. have responded similarly.

Saudi Arabia has condemned the Isreali invastion, pleged economic aid to Lebanon and sent a message to Sadat approving the call for a summit conference and stressing "the necessary of unifying Arab effort at thiscritical stage."