This term was originally taken from the physical concept of matter as composed of atoms, the smallest irreducible elementary particles in a void. This idea, which originates with Democritus and Epicurus, was adopted in the 19th century by economists to convey two ideas. The first, which has persisted, is the notion that individuals are many and unimportant. This has led to an assimilation in the French literature of ‘atomistic competition’ to ‘perfect competition’. However a second and more subtle idea was implied and received its clearest early expression in the work of Adam Smith. This is the concept of a society or economy as ‘atomistic’ rather than ‘organic’. Thus it is the actions of many independent individuals which determine the evolution of the whole, rather than the collective organization of these individuals. This idea was contested in particular by Marx, whose position was the opposite of that of the utilitarians.