In 1840 he published his treatise De l'humanite (2nd ed.
P. Laffitte, Les Grands Types de l'Humanite, vol.
- Fustel de Coulanges, La Cite antique (Paris, 1864); Lubbock, Origin of Civilization (1870); Whitney, Oriental and Linguistic Studies (New York, 1872 and 18 74); Brinton, The Religious Sentiment (1876); Myths of the New World' (New York, 1876); Essays of an Americanist (1890); Religions of Primitive Peoples (1897); Keary, Outlines of Primitive Belief (London, 1882); Leblois, Les Bibles et les initiateurs de l'humanite (4 vols.
He treated the relations of church and state in L'Eglise et Petal (Brussels, 3 vols., 1858-1862; new and revised edition, 1865), and the same subject occupied a large proportion of the eighteen volumes of his chief historical work, Etudes sur l'histoire de l'humanite (Ghent and Brussels, 1 8551870), which aroused considerable interest beyond the boundaries of Belgium.
The ambitious Bible de l'humanite (1864), an historical sketch of religions, has but little merit.
He published Les Grands Types de l'humanite (1875) and Cours de philosophic premiere (1889).