Plato therefore mentions two types of causes, “distinguishing those which possess understanding and thus fashion what is beautiful and good, from those which, when deserted by intelligence, produce only haphazard and disorderly effects every time” (Tim, 46e). Nonetheless, the Demiurge uses these lower, auxiliary causes (synaitia) to produce the best result possible (Tim, 46c). The properties of these contributing structures are unalterable by the Demiurge, which is the reason why persuasion by Intellect is required for creation to take place.122 Necessity is therefore a second principle (archē) in the origin of things (Tim, 48b), next to Intellect.
The phenomenon of necessity was naturally explored by such a keen observer of nature as Aristotle, who made a distinction between two kinds of necessity. On the one hand there is absolute necessity, which is manifested in eternal phenomena, and on the other hand there is hypothetical necessity, which is manifested in everything that is generated by nature and everything that is produced by art (PA I.639b). A conspicuous example of hypothetical necessity is animals requiring food to live (PA I.642a). An important instance of absolute necessity is circular motion, such as that of the sun which ensures the continuity of alternate generation and destruction (De Gen et Corr, II.338a). Many other natural phenomena are due to absolute necessity, flowing inevitably from the nature of the specific matter.123 The effects of gravity would be a notable example of absolute necessity. Whereas Aristotle thus views absolute necessity as unrelated to final causality (due to lacking purpose), the hypothetical necessity in nature provides the conditions for an explanation in terms of final causality.124
It was further reasoned by Aristotle that the formation of a person’s eye serves a certain purpose in accordance with the reason (logos) of the individual, while the color of the eye is incidental and must ‘of necessity’ (ex anangkēs) be ascribed to its matter and moving cause (GA, 778a–b). Sometimes necessity even opposes purpose, as in the case of monstrous births that are due to defective matter (GA, 767b).125 This reasoning implies that tragic conditions such as physical deformity and mental retardation are due to material imperfections that could not be overcome by the activity of Intellect.
Aristotle’s well-known insistence on final causality, or teleology, enables him to indemnify the Prime Mover (which is his conception of the divine Intellect) from the imperfections in nature. Thus, imperfections in the structure of animals are ascribed to defective material, not a defective maker. This phenomenon is due to the fact that matter is sometimes not suitable for the purpose in hand, Aristotle suggested. In their turn, imperfections in individual organisms are due to the inherent variability of matter, since the latter is formed of an endless variety of combinations of the four elements.126 Nevertheless, final causality cannot be ignored, he writes: “Both causes must be stated by the physicist, but especially the end; for that is the cause of the matter, not vice versa” (Phys II.200a). By recognising the role of both final causality and necessity in the physical world, Aristotle continues Plato’s notion that the cosmos is the product of the interaction between the divine Intellect and irrational Necessity.
The phenomenon of physical deformity has been explained by Thomas Aquinas in terms of Aristotelian causality: “For if the matter is not disposed to receive the agent’s imprint [i.e., the operation of the efficient cause] a defect will follow in the effect, as when monsters are born because of unprepared matter: the fact that it doesn’t transform and actualize the indisposed matter can’t be laid at the door of the agent, for agents have powers proportioned to their natures and their inability to go further can’t be called deficiency in power; we can say that only when its power falls short of the measure laid down by nature” (Summa contra Gentiles, 3.10).
Synthesis: The Combination of Intellect and Necessity
After describing the role of Necessity, Plato devotes the next part of the Timaeus to a discussion of the physical cosmos, which is presented as the offspring of the union of Intellect and Necessity. Stated the other way around, Intellect persuades Necessity to form the initial universe: “For the generation of this universe was a mixed result of the combination of Necessity and Intellect. Intellect overruled Necessity by persuading her to guide the greatest part of the things that become towards what is best; in that way and on that principle this universe was fashioned in the beginning by the victory of reasonable persuasion over Necessity” (Tim, 48a; Cornford’s translation). As Plato concludes, “That is why we must distinguish two forms of cause, the divine and the necessary” (Tim, 68e).
However, the result of the restriction of the activity of Intellect by irrational Necessity is that the physical world displays both design and accident, is both purposeful and contingent, and harbours both good and bad. This statement should not be confused with Gnostic dualism, according to which the world is inherently evil due to its creation by an inferior deity. In the traditional understanding, evil is not self-existing but follows from a privation of goodness, just as darkness is due to an absence of light.
Within this context of the interaction between Intellect and Necessity, Plato situates the constitution of the human being and the causal principles of its being. Earlier, in Book IV of the Republic, the various elements, or parts, of the individual soul had been sketched: the highest is reason, the lowest is appetite, and in between is thymos. The latter term is translated as any vehement passion, anger, or wrath, and in the good sense as spirit or courage.127 Now, in the Timaeus, Plato depicts the creation of the soul’s elements, as at least being a likely account (72d). The highest element, reason, is the immortal part of the soul and is therefore situated in the head, which is “the most divine part of us, and the master of all our other parts” (44d). This is followed by the creation of the mortal parts of the soul: the spirited part which is situated in the chest, and the appetitive part which is placed in the lower abdomen (69c–71a).
As a reflection of the intelligible and sensible realms of the cosmos, Plato thus conceives of the human being as consisting of two main components that differ essentially. On the one hand, there is the soul which participates in the realm of Ideas, and which is immortal and the bearer of Intellect. On the other hand, there is the body which is part of the sensible world, and which is mortal and represents the principle of Necessity in the human being.128 This anthropology would exercise an immense influence on Christian thought, in both the Greek and Latin traditions.
It has often been stated that the human body is a marvel of design, and in the case of religious believers this design is attributed to God. Now, if one considers the immense complexity and intricacy of organs such as the brain, the heart, and the eye, then the human body does appear to be marvellously designed. If, on the other hand, one considers the extreme susceptibility of the human body to an almost infinite range of illnesses and injuries during the entire lifespan between conception and death, a rather different picture emerges. One only has to think of the plethora of childhood diseases and bone fractures, the debilitating conditions appearing later in life, such as multiple sclerosis, diabetes, and arthritis, and the horrors of a whole range of cancers, as well as Alzheimer’s and Parkinson’s diseases.
There are two possible explanations for this organic ambivalence: either the human body was designed by God, in which case He would have to be held responsible for the prevalence of disease and physical suffering among humans; or the human body is the product of the interaction between the divine Intellect and irrational Necessity, in which case there is no blame or responsibility involved in this matter. We contend that the latter alternative, as taught by Plato and Aristotle, is the more accurate one,