( CNN ) -- There are certain moments of parental pride you know are coming : their first words , first steps , first date . And then there are the ones that blindside you . Like this : The night before the Nelson Mandela memorial service , my 13-year-old son said , `` Dad , I 'm going to wake up at 4 to watch the Mandela memorial . '' I was so proud that he was so inspired . He 's an all-star basketball player who mainlines ESPN . Now he wanted to get up in the middle of the night to watch CNN . Great success . And when President Obama spoke for our nation , I was grateful we 'd heard his remarks live . Obama captured President Mandela 's remarkable capacity to awaken activism . Across oceans , across continents , across racial divides , across generations , Mandela sparked what Robert F. Kennedy described to the South African people as `` ripples of hope . '' One of those ripples of hope inspired a skinny college kid with a funny name who 'd been more interested in rebounds than revolution . `` Over 30 years ago , '' Obama said , `` while still a student , I learned of Nelson Mandela and the struggles taking place in this beautiful land , and it stirred something in me . It woke me up to my responsibilities to others and to myself , and it set me on an improbable journey that finds me here today . '' Same here . Unlike our president , I was always interested in politics . ( As an athlete , I was small but slow . ) But at the University of Texas , something deeper happened . The Black Student Alliance erected shanties on the West Mall . They challenged their fellow Longhorns to take responsibility for UT 's role in apartheid . The university 's endowment , flush with billions of petrodollars , invested in corporations that did business in South Africa . That meant my ridiculously cheap tuition was in some way subsidized by profits from propping up apartheid . I learned names like Biko , Tambo , Sisulu , Tutu and of course , Mandela . Most important , I learned , as the Rev . Martin Luther King Jr. taught , that `` injustice anywhere is a threat to justice everywhere , '' that we are all tied into `` a seamless garment of destiny . '' It was thrilling to be a part , however infinitesimal , of something larger than myself . Even then , with my government on the side of apartheid , I knew we students were on the right side of history . I saved my `` Free Nelson Mandela '' t-shirt all these years . This week , I dug it out and showed my sons . I told them about the anti-apartheid movement and how , years later , I joined President Clinton in a White House meeting with Mandela , the prisoner-turned-president . We talked about the confidence that comes from knowing you 're on the right side of history . It is that same confidence that , I believe , was behind Obama 's decision to shake the hand of Cuban leader Raul Castro . Raul 's brother , Fidel , had been a steadfast supporter of Mandela 's African National Congress , even when the United States was on the wrong side of history . And Mandela never forgot a friend . That is not to excuse the horrendous human rights record of the Castro dictatorship . In his oppression , his censorship , his decades-long war on basic democratic rights , Fidel Castro was the anti-Mandela . I believe Obama shook Raul Castro 's hand for the same reason Reagan shook Gorbachev 's or Mandela shook that of F.W . de Klerk , the last president of an apartheid South Africa : because he knows he 's on the right side of history . Years ago , I accompanied Clinton to a meeting of the World Trade Organization in Geneva . Moments before the President was to speak , I peeked out into the audience , gasped and sprinted back to Clinton 's holding room . `` Mr. President , '' I said gravely , `` Fidel Castro is on the front row . '' No one had told us Castro would be there . Clinton was unflappable . `` Good , '' he said . `` Maybe he 'll learn something . '' Clinton stood before Castro and the other assembled world leaders and spoke confidently of `` a revolutionary idea : that freedom , freely elected governments , free markets , the free flow of ideas , the free movement of people ( are ) the surest route to the greatest prosperity for the largest number of people . '' I doubt Fidel actually learned much from Clinton 's speech . And I am not naive enough to believe Raul Castro will emulate Mandela simply because Obama shook his hand . But I do believe in the transformative , unpredictable power of sending out a ripple of hope from the right side of history . And I was thrilled that Obama 's ripple of hope bobbed over a sleepy seventh-grader in the predawn darkness , watching the arc of the moral universe bend toward justice . Join us on Facebook/CNNOpinion . The opinions expressed in this commentary are solely those of Paul Begala .
President Obama shook hands with Cuban leader Raul Castro at Mandela 's memorial . The two leaders exchanged a handshake and then took part in an official photo op before the president left for his trip to South Africa on Tuesday. Like Reagan shaking Gorbachev 's hands , Obama 's act makes sense . He says even a simple handshake can be potent and transformative . Begala : It sends out a ripple of hope from the right side of history .