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A telos (from the Greek for "end", "purpose", or "goal") is an end or purpose, in a fairly constrained sense used by philosophers such as Aristotle. It is the root of the term "teleology", roughly the study of purposiveness, or the study of objects with a view to their aims, purposes, or intentions. Teleology figures centrally in Aristotle's biology and in his theory of causes. The notion that everything has a telos also gave rise to epistemology. It is also central to some philosophical theories of history, such as those of Hegel and Marx.
Telos has been consistently used in Aristotle's writing several times to denote "goal". It is considered synonymous to the term teleute (end), particularly in Aristotle's discourse about the plot-structure in Poetics. The philosopher went as far as saying that telos can encompass all forms of human activity. This is demonstrated in the way one can say that the telos of warfare is victory or the telos of business is the creation of wealth. Within this conceptualization, there are telos that are subordinate to other telos since all activities have their respective goals. For Aristotle, these subordinate telos can become the means to achieve more fundamental telos. Through this concept, for instance, the philosopher underscored the importance of politics and that all other fields are subservient to it. He explained that the telos of the blacksmith is the production of a sword, while that of the swordsman's, which uses the weapon as a tool, is to kill or incapacitate an enemy. On the other hand, the telos of these occupations are merely part of the purpose of a ruler, who must oversee the direction and well-being of a state.
In contrast to telos, techne is the rational method involved in producing an object or accomplishing a goal or objective; however, the two methods are not mutually exclusive in principle. These are demonstrated in the cases of writing and seeing. In Martin Heidegger's analysis, the former is considered a form of techne since the end product lies beyond (para) the activity of producing while, in seeing, there is no remainder outside of or beyond the activity itself at the moment it is accomplished. Aristotle, for his part, simply designated telos as the consummation or the final cause of techne.
One running debate in modern philosophy of biology is to what extent teleological language (as in the "purposes" of various organs or life-processes) is unavoidable, or is simply a shorthand for ideas that can ultimately be spelled out non-teleologically. Philosophy of action also makes essential use of teleological vocabulary: on Davidson's account, an action is just something an agent does with an intention--that is, looking forward to some end to be achieved by the action. Action is considered just step necessary to fulfill human telos because it leads to habits. According to the Marxist perspective, historical change is dictated by socio-economic structures, which means that laws largely determine the realization of the telos of the class struggle.