Potentiality and actuality

These concepts, in modified forms, remained very important into the Middle Ages, influencing the development of medieval theology in several ways.

Joe Sachs renders it with the phrase "being-at-work" and says that "we might construct the word is-at-work-ness from Anglo-Saxon roots to translate energeia into English".

According to Sachs (1995, p. 245): Aristotle invents the word by combining entelēs (ἐντελής, 'complete, full-grown') with echein (= hexis, to be a certain way by the continuing effort of holding on in that condition), while at the same time punning on endelecheia (ἐνδελέχεια, 'persistence') by inserting telos (τέλος, 'completion').

This is a three-ring circus of a word, at the heart of everything in Aristotle's thinking, including the definition of motion.Sachs therefore proposed a complex neologism of his own, "being-at-work-staying-the-same.

A major difficulty comes from the fact that the terms actuality and potentiality, linked in this definition, are normally understood within Aristotle as opposed to each other.

[19] In an influential 1969 paper, Aryeh Kosman divided up previous attempts to explain Aristotle's definition into two types, criticised them, and then gave his own third interpretation.

In a more recent paper on this subject, Kosman associates the view of Aquinas with those of his own critics, David Charles, Jonathan Beere, and Robert Heineman.

[28] This means that as well as its central role in his physics and metaphysics, the potentiality-actuality distinction has a significant influence on other areas of Aristotle's thought such as his ethics, biology and psychology.

"[31] In the Metaphysics, Aristotle wrote at more length on a similar subject and is often understood to have equated the active intellect with being the "unmoved mover" and God.

Students of the history of philosophy continue to debate Aristotle's intent, particularly the question whether he considered the active intellect to be an aspect of the human soul or an entity existing independently of man.

Polybius about 150 BC, in his work the Histories uses Aristotle's word energeia in both an Aristotelian way and also to describe the "clarity and vividness" of things.

[34] Already in Plato it is found implicitly the notion of potency and act in his cosmological presentation of becoming (kinēsis) and forces (dunamis),[35] linked to the ordering intellect, mainly in the description of the Demiurge and the "Receptacle" in his Timaeus.

[36][37] It has also been associated to the dyad of Plato's unwritten doctrines,[38] and is involved in the question of being and non-being since from the pre-socratics,[39] as in Heraclitus's mobilism and Parmenides' immobilism.

The mythological concept of primordial Chaos is also classically associated with a disordered prime matter (see also prima materia), which, being passive and full of potentialities, would be ordered in actual forms, as can be seen in Neoplatonism, especially in Plutarch, Plotinus, and among the Church Fathers,[39] and the subsequent medieval and Renaissance philosophy, as in Ramon Lllull's Book of Chaos[40] and John Milton's Paradise Lost.

In his Enneads he sought to reconcile ideas of Aristotle and Plato together with a form of monotheism, that used three fundamental metaphysical principles, which were conceived of in terms consistent with Aristotle's energeia/dunamis dichotomy, and one interpretation of his concept of the Active Intellect (discussed above): This was based largely upon Plotinus' reading of Plato, but also incorporated many Aristotelian concepts, including the unmoved mover as energeia.

[42] Other than incorporation of Neoplatonic into Christendom by early Christian theologians such as St. Augustine, the concepts of dunamis and ergon (the morphological root of energeia[43]) are frequently used in the original Greek New Testament.

[47] In contrast, the position of Western Medieval (or Catholic) Christianity, can be found for example in the philosophy of Thomas Aquinas, who relied on Aristotle's concept of entelechy, when he defined God as actus purus, pure act, actuality unmixed with potentiality.

Francis Bacon in his Novum Organon in one explanation of the case for rejecting the concept of a formal cause or "nature" for each type of thing, argued for example that philosophers must still look for formal causes but only in the sense of "simple natures" such as colour, and weight, which exist in many gradations and modes in very different types of individual bodies.

[49] In the works of Thomas Hobbes then, the traditional Aristotelian terms, "potentia et actus", are discussed, but he equates them simply to "cause and effect".

The definition of energy in modern physics as the product of mass and the square of velocity, was derived by Leibniz, as a correction of Descartes, based upon Galileo's investigation of falling bodies.

He preferred to refer to it as an entelecheia or 'living force' (Latin vis viva), but what he defined is today called kinetic energy, and was seen by Leibniz as a modification of Aristotle's energeia, and his concept of the potential for movement which is in things.

[51] Leibniz wrote:[52] ...the entelechy of Aristotle, which has made so much noise, is nothing else but force or activity; that is, a state from which action naturally flows if nothing hinders it.

But matter, primary and pure, taken without the souls or lives which are united to it, is purely passive; properly speaking also it is not a substance, but something incomplete.Leibniz's study of the "entelechy" now known as energy was part of what he called his new science of "dynamics", based on the Greek word dunamis and his understanding that he was making a modern version of Aristotle's old dichotomy.

"As 'a science of power and action', dynamics arises when Leibniz proposes an adequate architectonic of laws for constrained, as well as unconstrained, motions.

A soul, or spirit, according to Leibniz, can be understood as a type of entelechy (or living monad) which has distinct perceptions and memory.

[54][55] As discussed above, terms derived from dunamis and energeia have become parts of modern scientific vocabulary with a very different meaning from Aristotle's.

As mentioned above, the concept had occupied a central position in the metaphysics of Leibniz, and is closely related to his monad in the sense that each sentient entity contains its own entire universe within it.

In the biological vitalism of Hans Driesch, living things develop by entelechy, a common purposive and organising field.

Leading vitalists like Driesch argued that many of the basic problems of biology cannot be solved by a philosophy in which the organism is simply considered a machine.

One example was the American critic and philosopher Kenneth Burke (1897–1993) whose concept of the "terministic screen" illustrates his thought on the subject.