He studied Law at the University of Athens and then continued his studies in Germany, France and England. He was associated with the circle of the demoticists and progressive intellectuals of the time. In 1908 he founded the‘Sociological Society‘. He joins the military movement of Wudi in 1909. The following year he founded the People’s Party. He is elected as a deputy of Arcadia. He works for the expropriation of agricultural land belonging to the old farms.
He participated as a volunteer in the Balkan wars and was decorated for his bravery. He joins the movement of Elef. In 1915, he joined the Eleventh Venizelos movement (1915) and took over the Ministry of Transport, which he held until 1920, then the Ministry of Supply and Interior. In 1922 he participated in the drafting of the “Democratic Manifesto” calling on King Constantine to abdicate in order to prevent the Treaty of Sevres from being overturned. He is sentenced to 3 years’ imprisonment in Lamia.
After the Asia Minor disaster he founds the party of the “Democratic Union – Peasant and Labour Party”. Papanastasiou proclaims the need for an unrestricted democracy (1923) in the elections of the 4th National Constituent Assembly. He became Prime Minister in 1924 and proclaimed the constitution of the unconstitutional republic, which was ratified by a referendum with 70% of the votes, hence the nickname“Father of Democracy“.
In 1924 he turned against the dictatorship of Th. He was arrested and deported. In 1926 he was elected MP for Mantinea and became Minister of Agriculture until 1928. In 1932 he forms a government of personalities, becomes Minister of Agriculture and National Economy. He opposes the 1935 movement, is imprisoned at the restoration of Basel, is acquitted and is again deported.
In 1936 he was elected again as a deputy, but he opposed and refused a vote of confidence in Metaxas. Papanastasiou’s work was immense, we enumerate: he laid the foundations of group transport (means of transport), postal services and telegraphy. He established the national cadastre, building regulations, a regulatory plan of the city of Athens. He established the International Committee for the Reconstruction of Thessaloniki. Founded the University of Thessaloniki (1924). Reorganized the NTUA and the School of Fine Arts.
Philothechus helps to enrich the National Gallery. Close friend of all writers and artists (K. Parthenis, K. Palamas, Al. Delmouzos, M. Kalomiris, Ag. Sikelianos, etc.). He organized the Agricultural Cooperatives and schools of agricultural education. He founded the Agricultural Bank. He created the Areos Field as a Park, opened the doors of the Royal Garden and renamed it the National Garden.
Ideologically, he was deeply democratic, innovative and pioneering for his time, such as: on issues of civil marriage, women’s suffrage, protection of maternity, illegitimate children, social security, abolition of the death penalty, separation of church and state, trade union and cooperative organisation, voting by simple proportional representation, etc.For all this, he could not accept authoritarianism and dictatorial movements, which was common for the time. He was also in favour of equal cooperation between states and helped to create the Balkan Union and Greek-Turkish friendship between El. Venizelos and Kemal Atatürk (1930-1933). C. Papandreou said: ‘Venizelos realised in Greece the nation and the state. Al. Papanastasiou introduced to it the spiritual and social character. He was an encyclical of the political world of Greece. As virtuous as any man, as cheerful as any man.