The phrase "all that is solid melts into air" is often associated with Marx´s ideas and appears in the works of Friedrich Engels, Marx's collaborator. The specific formulation is found in the Communist Manifesto, published in 1848. The relevant passage is as follows:

"All fixed, fast-frozen relations, with their train of ancient and venerable prejudices and opinions, are swept away, all new-formed ones become antiquated before they can ossify. All that is solid melts into air, all that is holy is profaned, and man is at last compelled to face with sober senses his real conditions of life and his relations with his kind."

In this context, Marx and Engels are describing the transformative effects of capitalism on social structures and relationships. The phrase suggests that the established and traditional institutions, relationships, and social hierarchies that characterized feudal societies were being rapidly dissolved by the forces of industrial capitalism.

Here's an analysis of the key concepts in the passage:

This idea aligns with Marx's broader analysis of historical materialism and the dialectical process of societal change. The transition from feudalism to capitalism is characterized by the upheaval of existing social relations and the emergence of new forms of production and social organization. The phrase has been widely cited and interpreted in various ways, reflecting its resonance in discussions of social and economic transformation.