Arias Calderón was born on May 4, 1933, and studied humanities and philosophy. But he was known for his fierce opposition to the military dictatorship, headed first by Omar Torrijos and finally by Manuel Antonio Noriega. For many years, he presided over the Christian Democratic Party, now the Partido Popular.
He was also part of the Civil Crusade that fought for the reestablishment of democracy. In 1989 he was the vice presidential candidate of the Democratic Alliance of Civilian Opposition, that won elections that the Noriega regime would declare void.
After the US invasion in December 1989 that overthrew Noriega, he took power alongside Endara and Ford. He served as Minister of Government and Justice, and promoted the constitutional reform for the elimination of the army.