Four causes
The four causes or four explanations are, in Aristotelian thought, four fundamental types of answer to the question "why?" in analysis of change or movement in nature: the material, the formal, the efficient, and the final. Aristotle wrote that "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause."[1][2] While there are cases in which classifying a "cause" is difficult, or in which "causes" might merge, Aristotle held that his four "causes" provided an analytical scheme of general applicability.[3]
See also: Potentiality and actuality
Aristotle's word aitia (Greek: αἰτία) has, in philosophical scholarly tradition, been translated as 'cause'. This peculiar, specialized, technical, usage of the word 'cause' is not that of everyday English language.[4] Rather, the translation of Aristotle's αἰτία that is nearest to current ordinary language is "explanation."[5][2][4]
In Physics II.3 and Metaphysics V.2, Aristotle holds that there are four kinds of answers to "why" questions:[2][5][6]
The four "causes" are not mutually exclusive. For Aristotle, several, preferably four, answers to the question "why" have to be given to explain a phenomenon and especially the actual configuration of an object.[7] For example, if asking why a table is such and such, an explanation in terms of the four causes would sound like this: This table is solid and brown because it is made of wood (matter); it does not collapse because it has four legs of equal length (form); it is as it is because a carpenter made it, starting from a tree (agent); it has these dimensions because it is to be used by humans (end).
Aristotle distinguished between intrinsic and extrinsic causes. Matter and form are intrinsic causes because they deal directly with the object, whereas efficient and finality causes are said to be extrinsic because they are external.[8]
Thomas Aquinas demonstrated that only those four types of causes can exist and no others. He also introduced a priority order according to which "matter is made perfect by the form, form is made perfect by the agent, and agent is made perfect by the finality."[9] Hence, the finality is the cause of causes or, equivalently, the queen of causes.[10]
In the Scholasticism, the
efficient causality[35] was governed by two principles:
Thomas in this regard distinguished between causa fiendi (cause of occurring, of only beginning to be) and causa essendi (cause of being and also of beginning to be)[39][43] When the being of the agent cause is in the effect in a lesser or equal degree, this is a causa fiendi.[44]
Furthermore, the second principle also establishes a qualitative link: the cause can only transmit its own essence to the effect. For example, a dog cannot transmit the essence of a feline to its young, but only that of a dog.[45] The principle is equivalent to that of Causa aequat effectum (cause equals effect)[46] in both a quantitative and qualitative sense.