Teleology (from the Greek, telos - purpose or end) is the philosophical idea of design, purpose and goal-directed intention.
Aristotle stated that "Men do not think they know a thing till they have grasped the 'why' of it (which is to grasp its primary cause)". Teleology comes for the Greeks as a natural reaction to Causality - if causes did not have effects, the very concept of primary causes would be meaningless. Plato, in the Phaedo, drew a distinction between efficient causes and what Aristotle would end up calling final causes. Efficient causes are the immediate causal step that enable something to happen. A car reversing accidentally drives over my foot - the cause of the immense pain in my foot would have as it's efficient cause the car parked on it. But this is not the final cause. If a person were to commit an intentional hit-and-run, then the efficient cause would be the same - the car hitting the person - but the final cause would be the intention or design of the driver. When we discuss a crime - a murder, say, it does not matter a tremendous amount how the crime was committed.
Plato showed a strange problem with teleology, namely that we often do things which have as their cause things in the future. A student learns to structure essays well while in school, so that when they get to university, they can pass their examinations. Without the concept of a mind or consciousness directing this, the earlier action does not make much sense. At a simple level, this is not controversial. It is certainly a strange way of looking at it that the driving of a car is the cause of having to find one's car keys. At another level, it becomes more controversial. If our minds are the cause of goal-directed action, then, as Michael Ruse puts it, "Whose mind is it that puts everything in motion and orders things for their own good? It is hardly our own minds - at least, it is hardly our minds once we look beyond our intentions and desires. We did not decree that eating would be of importance in achieving growth and maturity". Plato points to God, or the Demiurge (the sense of divine creative purpose which Plato describes in the Timaeus).
In modern philosophy, the notion of a final cause has had rough treatment. Francis Bacon described the use of final causes within science as being irrelevant to scientific inquiry - they have "given men the occasion to stay upon these satisfactory and specious causes, to the great arrest and prejudice of further discovery". Descartes similarly did not deny the existence of a divinely-sourced final cause, but noted that we should not seek it, rather focusing on the efficient cause.
- Aristotle's Physics Book 2, Chapter 3
- Michael Ruse, Darwin and Design: Does evolution have a purpose?, Harvard University Press, 2003, p. 14
- Francis Bacon, 1605, The Advancement of Learning