Boathouse or houseboat: how your mind snaps simple ideas together
Put 'boat' and 'house' together one way and you get a shed for boats; flip them and you get a floating home. Concepts are the building blocks behind that trick. They let you recognise a bristled plastic stick as a toothbrush instantly and tell edible plants from poisonous ones without thinking.
A concept is a basic unit of thought that sorts things into kinds and captures what they share. The idea of a prime number, a teacher or a car tells you what members of each group have in common. Philosophers separate a concept's intension, the features it encodes, from its extension, everything it picks out. 'City' covers Paris and Tokyo; 'Mars' names one planet; 'unicorn' refers to nothing at all. The English word comes from the Latin concipere, to take in, and is first recorded in 1479.
Concepts are pieces of thought rather than whole thoughts. 'Baby' asserts nothing until it becomes 'the baby is sleeping'. They also differ from raw sensation: you can see the difference between two shades of red without having a separate idea for each. Nor are they the same as words, since one word can carry several meanings and a person can grasp a concept without knowing any name for it. Some nonhuman animals appear to form them too.
Their practical payoff is enormous. Sorting things into categories trims the world's complexity, usually fast and unconsciously. Once something is recognised as a shovel, you can predict it is for digging. A crowd chanting and waving scarves makes sense once classified as football fans, and a doctor moves from symptoms to diagnosis to treatment by chaining concepts together. Hierarchies help as well: every fox inherits what makes something a mammal, and every mammal what makes something an animal.
How concepts work inside the mind is contested. The classical theory treats them as definitions with strict rules. Prototype theory says membership depends on resemblance to a typical example, while exemplar theory relies on memories of specific instances. Others embed concepts in wider theories or treat word-level concepts as unstructured atoms. Nativists and empiricists still argue over whether any are inborn, though children clearly master concrete ideas like 'apple' before abstract ones like 'infinity'.
Source: Concept
