Valentí Almirall's *Lo Catalanisme* is a foundational work of Catalan nationalism, first published in the late 19th century. The book explores the concept of 'particularism', advocating for a decentralized Spain with greater autonomy for Catalonia. Almirall draws parallels with federalist systems like the United States and Switzerland, arguing that such a structure would benefit both Spain and Catalonia. This work had a significant impact on the development of Catalan political thought in the early 20th century, influencing the emergence of both conservative and leftist movements within Catalanism.