Materials in eighteenth-century science: contexts and practices -- Commodities and natural objects -- Practices of studying materials in eighteenth-century chemistry -- Why study classification? -- A world of pure chemical substances -- 1787: a new nomenclature -- The Tableau de la nonmenclature chimique -- Classifying according to chemical composition -- Simple substances and paradigmatic syntheses -- Operations with pure chemical substances -- Classification of pure chemical substances before 1787 -- A revolutionary table? -- A different world: plant materials -- Diverse orders of plant materials -- Ultimate principles of plants: plant analysis prior to 1750 -- The epistemic elevation of vegetable commodities -- The failure of Lavoisier's plant chemistry -- Uncertainties -- A novel mode of classifying organic substances and an ontological shift around 1830 -- Conclusion: Multidimensional objects and materiality.