The study of the ends or purposes of things. The idea that there is such a thing as the end or purpose of life is prominent in the Aristotelian view of nature (and ethics), and thence in the Christian tradition. The association with moral thought is visible in the idea that correct human living is in accordance with natural law, or in the idea that human nature can only fulfil its purpose through the exercise of virtue. The theory of evolution through natural selection allows speculation about the function for which particular things are adapted, and so permits assertions about the purpose an adaptation serves, without any commitment to the idea of a designer who put it there for a purpose, and without the unscientific belief that the future utility of a feature somehow brings about its existence by a kind of backward causation. Teleology free of these implications is sometimes called teleonomy. The teleology of a feature may have metaphysical implications: thus one might (controversially) suggest that our spatial vision is for success at coping with a spatial world, whereas colour vision may not be for success at coping with a coloured world, but adapted to the skilful tracking of surfaces through changes of light, and this would be a way of defending a primary/secondary quality distinction. See also function, biological.