Luis Posada Carriles and Ernesto Guevara were born in 1928 in similar environments. Both were part of the upper middle-class. Both chose the sciences during their college years. Guevara studied medicine; Posada, chemistry. Both shared a bold and adventurous psychological makeup that would lead them to risk their lives and sacrifice the welfare of their families to defend -- violently -- their beliefs.

Fidel Castro joined these two personalities in parallel lives. After Batista's military coup in 1952, Castro became the most important figure of the armed opposition when he created the July 26 Movement to overthrow the dictator and achieve power. Che and Posada were in that organization. The Argentine, in the Sierra Maestra; the Cuban, in the clandestine struggle.

Around that time, ''the 26'' practiced indiscriminate terrorism in public sites. In November 1958, the group carried out the first hijacking of a civilian airplane for political purposes, an abominable crime that took the lives of numerous victims when the aircraft crashed in the Bay of Nipe. The Castro-inspired terrorism was so intense that old residents of Havana still remember ''the night of 100 bombs'' and the savage blasts of explosives in social halls and hotels, set by perpetrators who cared nothing about the harm they wreaked on innocent people.

That was the lamentable moral and political atmosphere in Cuba at that time. The means didn't matter if the ends seemed justifiable. In the Sierra Maestra, Che did not hesitate to blow off the head of any peasant who was even remotely suspected of collaborating with Batista's army.

He even wrote an amazing statement that summarizes the implacable logic of the revolutionary: ``Hatred as a factor of the struggle, an intransigent hatred for the enemy, pushes man beyond his natural limitations and turns him into an effective, violent, selective and cold killing machine. Our soldiers must be like that; people without hatred cannot triumph over a brutal enemy.''

When Fidel Castro and a few other leaders shifted the course of their government and sailed toward communism and an alliance with Moscow, Cuba plunged right into the Cold War. The country and the July 26 Movement split in two. Posada Carriles joined the armed band of those who defended democracy at gunpoint, while Che Guevara, also at gunpoint, defended communism. Posada believed (and fought for his belief) that the happiest societies resembled the United States or Canada. Che was certain that the ideal model was Mao's dictatorship.

The Cuban government sought the support of the KGB. Posada and hundreds of former members of the July 26 Movement, veterans of the Bay of Pigs, placed themselves under the direction of the CIA. Guevara went to Africa to try to create new communist tyrannies in the old European colonies. Posada and other Cubans went there to fight against Che's men to prevent it. On Lake Tanganyika, Cubans confronted Cubans. That time, the exiles won.

The same happened in Venezuela in the 1960s. Castro tried to terminate Venezuela's fragile democracy. At the CIA's urging to the Caracas government, Posada went to fight the communist guerrillas fed from Havana. The communists lost that war. A short while later, in Bolivia, Che was captured and executed.

The Cold War then turned more violent. Cuba became the training center for the world's worst terrorists. Venezuelan-born Carlos Ilich Ramírez, aka ''the Jackal,'' went through those training camps. Shortly thereafter, he hijacked airplanes and in 1972 organized the murder of the Israeli athletes during the Munich Olympics.

Four years later in Venezuela, a plot was hatched to blow up a Cuban airliner in flight. It was a monstrous act that took 73 lives. Posada denies any connection to the deed. He was accused and absolved, but was kept in prison while the government appealed the ruling. Two Venezuelans were sentenced.

Thereafter, Posada escaped from prison. He assumed the name Ramón Medina and again linked up with the CIA to continue his interminable battle. The agency hired him to help the Nicaraguan guerrillas, who, with Washington's backing, fought against the tyranny of Daniel Ortega. Thanks to President Reagan's implacable opposition, the communists were defeated in the region.

Posada turned his eyes to his native land. His efforts had been successful everywhere, except in Cuba. It was then -- it is alleged; Posada denies it -- that a plan was launched to execute Castro abroad and interrupt the flow of tourists with bombs in hotels and social halls, just like ''the 26'' had done half a century earlier.

Ironically, it was the government of the United States that put an end to Posada's adventure-filled life and confined him in a sort of house arrest before a federal judge dropped all charges against him and set him free.

Nobody understands why the media in the West are less harsh on Guevara than on Posada. Nobody wears a T-shirt with the effigy of Posada, after all. There is something basically hypocritical in all this. A double standard.