The early 1870s saw Labriola take up journalism, and his writings from this time expressed liberal and anticlerical views.

In 1874, Labriola was appointed as a professor in Rome, where he would spend the rest of his life teaching, writing, and debating.

Although he had been critical of liberalism since 1873, his move towards Marxism was gradual, and he did not explicitly express a socialist viewpoint until 1889.

He saw Marxism not as a final, self-sufficient schematisation of history, but rather as a collection of pointers to the understanding of human affairs.

These pointers needed to be somewhat imprecise if Marxism was to take into account the complicated social processes and variety of forces at work in history.