A year and a half ago Lucio Magri, one of Italy's most respected leftwing intellectuals, flew to Switzerland, entered a clinic and drank the fatal hemlock; in his case it meant swallowing a death pill. For a few days most of Italy was in shock. Suddenly Magri was everywhere. Parliament observed a minute's silence, newspaper comment was broadly sympathetic, but his closest friends were unhappy. His wife had died after a long illness two years earlier, and had discouraged Magri from following suit, insisting that he finish his book on the fate of Italian communism. With The Tailor of Ulm completed and published, he decided to say farewell to life. The loss of his wife was the trigger, but there were other reasons. He no longer felt contemporary.

Italian communism and those on its left had committed political suicide. A bankers' clique governed the country, with the staunch backing of an octogenarian, ex-communist president, the left intelligentsia had collapsed – so what was the point of living? Most of his friends were unconvinced, even angry. They tried to talk him out of it, but Magri was unmoved. "To be true, simply true," Stendhal once wrote, "that is the only thing that matters." For Magri, truth meant taking his own life. He was neither the first nor the last to depart in this fashion.

It reminded me of a short pamphlet I had read over four decades ago. The Last Words of Adolf Abramovich Joffe (published by the Lanka Sama Samaja Party, Ceylon, 1950). It was a suicide note dated 16 November 1927, and addressed to Leon Trotsky. After completing it, Joffe, one of the most trusted of Soviet diplomats, put a pistol to his head and pressed the trigger. What struck me at the time was not so much the suicide itself but the human qualities on display, visible in the first few paragraphs: "Dear Leon Davidovich: All my life I have thought that the man of politics ought to know how to go away at the right time, as an actor quits the stage, and that it is better to go too soon than too late.

"More than 30 years ago I embraced the philosophy that human life has meaning only to the degree that, and so long as, it is lived in the service of something infinite. For us humanity is infinite.

"The rest is finite, and to work for the rest is therefore meaningless. Even if humanity too must have a purpose beyond itself, that purpose will appear in so remote a future that for us, humanity may be considered as an absolute infinite. It is in this and this only that I have always seen the meaning of life.

"And now, taking a glance backward over my past, of which 27 years were spent in the ranks of our party, it seems to me that I have the right to say that during all my conscious life I have been faithful to this philosophy. I have lived according to this meaning of life: work and struggle for the good of humanity. I think I have the right to say that not a day of my life has been meaningless. But now, it seems, comes the time when my life loses its meaning, and in consequence I feel obliged to abandon it, to bring it to an end …"

One reason why Joffe – a physician by training – had quit the stage was his illness. On Stalin's instructions, the Kremlin doctors refused to treat him and the Politburo refused to sanction the money needed to go abroad. Why? Because in those chaotic and disconcerting times, Joffe was a dissident, a leading member of the Left Opposition, a grouping of the Bolshevik old guard – led by Trotsky, Grigory Zinoviev, Lev Kamenev – that united after Lenin's death to combat Stalinist policies and practices. They were outmanoeuvred, defeated and expelled from the leadership and then the party itself. Repelled by the factional fury unleashed against them, Joffe, unlike many others, refused to observe and move on. For men like him, silence was never an option. It was synonymous with submission, and the integrity of one's inner life could not remain immune from the storms raging outside.

Joffe had watched as the opposition negotiated, compromised and accepted the decision of the party, right or wrong. Trotsky had, at that point, not favoured the idea put forward by some of his supporters: a total break with Stalin's faction and the announcement of a new party. The oppositionist Karl Radek wrote in a letter to his comrades that in reality what they had done was to have confine themselves to choosing "between two forms of political suicide": either to be politically isolated from the party or to capitulate and re-enter on Stalin's terms. The latter would later be Radek's own choice, and that of others.

Joffe's letter had reproached Trotsky for conciliationism: "But you have often renounced your right position in favour of an agreement, a compromise, whose value you overestimated. That was wrong … don't be afraid today if certain ones desert you, and especially if the many do not come to you as quickly as we all wish. You are in the right, but the certainty of the victory of your truth lies precisely in a strict intransigence, in the most severe rigidity, in the repudiation of every compromise, exactly as that was always the secret of the victories of Ilych [Lenin] … I have often wanted to tell you this, and have only brought myself to it now, at the moment of saying goodbye … "

In today's world the political passions and generous impulses revealed in Joffe's letter read as if he were writing from Atlantis. But it is part of a history that dominated the preceding century, and as we approach the centenary of the Russian revolution, it deserves to be remembered. Joffe's widow Maria survived the camps, and after Stalin's death left the Soviet Union and moved to Israel. Her book, One Long Night – A Tale of Truth, remains one of the many affecting memoirs from that time.