Fallacy of Composition

The fallacy of composition is committed when one infers that a collection of things must have the same properties as the individual elements of which the collection is composed. Such reasoning is fallacious because it is possible for a collection to have very different properties than do any of its constituent members, and therefore one cannot simply make inferences about the properties of the whole based upon the properties of its parts. To illustrate, some examples of collections with properties different to their constituent elements are given below:

  • A pile of sand may be 20cm tall, but obviously that doesn’t imply that the individual grains of sand that comprise the pile are also 20cm tall.
  • Individual water molecules are not ‘wet’, as ‘wetness’ is a property that only makes sense with reference to the behaviour of a large number of water molecules.
  • Cells are alive, and cells are composed entirely of organic and inorganic compounds, however those chemical compounds are not themselves alive.
  • An object like a desk is solid, even though it is made up of atoms which themselves are not ‘solid’ at all, but are mostly empty space.
  • An individual ant is quite a simple animal which acts mostly in accordance with basic instincts, however a colony of ants is can build elaborate nests and engage in wars with other colonies, all behaviours which are outside the ability and understanding of any single ant.

The fallacy of composition is one of the most subtle logical fallacies, and as such it can often appear unexpectedly in arguments which otherwise sound quite compelling. This fallacy often arises in the context of philosophical arguments about consciousness, moral value, free will, goodness, and other such abstract properties. It is sometimes argued that, at least under a materialist worldview, humans are just very complex machines made up of atoms, and since atoms do not have consciousness/moral value/free will/etc, then neither do humans. This is an instance of the fallacy of composition since, as we have seen, collections (including collections of atoms) can possess properties that the individual components of the collection lack. The fallacy is also often seen in political or economic debates, where it is sometimes argued that because some outcome or action is difficult or undesirable for individuals, that action or outcome is therefore similarly difficult or undesirable for a nation of individuals. This is fallacious reasoning because nations (being collections of individuals) can possess properties different from any individual – for example, individual humans are mortal while nations can last indefinitely.

Further Reading

Fallacy of composition: overview from Logical Fallacies

Fallacy of composition: overview from Nikor Project

Fallacy of composition: overview from Logically Fallacious

Fallacies of composition and division: overview with useful examples from The Logical Place