His thought combines elements of pantheism and millenarism, an ethic of renunciation (like in Buddhism or Franciscanism), and a belief in freedom as the most important feature of man.

[1] He is part of a tradition of visionary thought that includes Father António Vieira and the poets Luís de Camões and Fernando Pessoa.

In 1933 he commenced teaching at Aveiro high school but was discharged in 1935 for refusing to sign a statement—then mandatory to all civil servants—which renounced participation in secret (thus subversive) organizations.

He returned to Portugal in 1969 after Salazar's illness and replacement by Marcello Caetano, which created some political and cultural opening in the regime.

In 1990, the Portuguese public television channel RTP1 broadcast a series of thirteen interviews with him entitled Conversas Vadias.

A documentary entitled Agostinho da Silva: Um Pensamento Vivo, directed by João Rodrigues Mattos, was released by Alfândega Filmes, in 2004.

There is an unreleased interview by António Escudeiro entitled Agostinho por Si Próprio, where he talks about the worship of the Holy Spirit.

Among his works are biographies of Michelangelo, Pasteur and St. Francis of Assisi; his most influential book may be Sete Cartas a Um Jovem Filósofo (Seven Letters to a Young Philosopher).