This post serves as an attempt to outline the differences between a classical Aristotelian view of the world and that of the great early modern, philosopher, Rene Descartes. The purpose of these essays will help us understand how and why these differences in understanding the nature of reality matter, primarily with how we understand purpose, or teleology in the world. Cartesian philosophy is still very much present in our current intellectual climate and still has an impact on the way we view the nature of things and individuals in the world around us.  Here’s where we left off …

In this conversation, it is helpful to understand that Aristotle’s conception of act and potency are important corollaries to his notion of cause, and are necessary to understand Descartes’ position on final causation and the resulting Cartesian conception of the world. With Aristotle’s construct of act, potency, and causation in place, the discussion between Aristotle and Descartes regarding final cause becomes clear. Act is that which has actual existence in this world. Potency is all the possibilities something could undergo in the world of becoming (For sake of brevity, Aristotle’s conceptions of act and potency related to cause can be found in Aristotle’s Metaphysics, pg. 538, 565-566, and 569-575, among other places. This discussion is a quick summary). These are central concepts for Aristotle as he explains change and the causes of change in the world. With the exception of universals, virtually all things of the physical world are subject to change or movement. Both living and non-living things experience change. Change is the actualization of a thing’s potential. According to Aristotle, change is potency reduced to act. However, an outside and additional element is necessary to bring about change. Something else, always itself in “act,” is needed to actualize a potential. Potency, itself, cannot bring about act—just as non-being cannot bring about being. For Aristotle, act and potency are as fundamental as Being and Becoming, but to explain change more clearly, he provides the famous four causes which help clarify why that which reduces potential to act is called a cause. The first cause is the material cause—that out of which something is actualized The second cause is the efficient cause—that by which something is actualized. The third cause is the formal cause—that into which something is actualized. The fourth cause is the final cause—that for the sake of which something is actualized. A biological example will help explain how these four causes work in the physical world. To understand the basics of the human heart, it is important to know what it is made of—its material cause. In this case, the material cause of a heart is muscle. The efficient cause rests in the DNA that structured and ordered cells in such a way as to create a muscular heart and not a kidney or spleen. The formal cause is that which the heart muscle is fashioned into—ventricles, arteries, aorta, etc. The final cause serves the purpose of pumping blood. Aristotle sees purpose or goal-directedness wherever cause and effect relationships take place in this world, and is a significant element of his philosophy. The totality of the three previous causes all serve a goal or ultimate end, culminating in the final cause. Focusing on act and potency, the efficient cause is that which actualizes a potency. The final cause is that which actualizes the purpose or the reason something is actualized. In human activity things are done with intentionality, and the possibilities we speak of regarding human beings are often referred to as human potential. As we shall see, Descartes, in the end, reduces much of Aristotle’s causes to the efficient cause.

Note: Interestingly, Aristotle does not seem to use the same order of his four causes. On page 128, this order is given: formal, material (in this particular case—“an antecedent which necessitates consequent”), efficient, and final. On pages 514-515, the order is: efficient, final, material, formal. And on page 271, we see this order: material, formal, efficient and final. However, on page 514, Aristotle points to the goal-directedness of changeable things and their causes, “For how can a principle of change or the nature of the good exist for unchangeable things, since everything that in itself and by its own nature is good is an end, and a cause in the sense that for its sake the other things both come to be and are, and since an end or purpose is the end of some action, and all action simply change” (514)? In general, Aristotle sees the final cause as an ultimate goal-directed end.

Descartes, on the other hand, is skeptical of Aristotle’s conclusions and is not certain whether or not final cause can be discerned in reality. He does not completely deny the existence of final causality, but he thinks such knowledge transcends his abilities, “I have no further difficulty in recognizing that there is an infinitude of matters in His power, the causes of which transcend my knowledge; and this reason suffices to convince me that the species of cause termed final, finds no useful employment in physical [or natural] things; for it does not appear to me that I can without temerity seek to investigate the [inscrutable] ends of God” (316). As he explains to one of his objectors, Descartes elucidates further:

The arguments you adduce on behalf of final causality are to be referred to the efficient cause; thus it is open to us, from beholding the uses of the various parts in plants and animals to regard with admiration the God who brings these into existence, and from a survey of His works to learn to know and glorify the author of these works, but that does not imply that we can divine the purpose for which he made each thing. And although in Ethics, where it is often allowable to employ conjecture, it is at times pious to consider the end which we may conjecture God set before Himself in ruling the universe, certainly in Physics where everything should rest upon the securest arguments, it is futile to do so. We cannot pretend that certain of God’s purposes, while, as to those which you have brought forward in illustrating the difficulty in question, there is no one who does not think that he is acquainted with them (441).

As a devout Roman Catholic, it is clear that Descartes is skeptical of the notion of final causality because he does not want to be so arrogant as to claim to know the mind of God. On the other hand, Aristotle might ask, how is it arrogant or impious to say that the eye is for seeing, the heart is for pumping blood, and human beings always do something with some good in mind? And why is it necessary to completely rule out the idea of final cause in physics? At this point, it seems that Descartes and Aristotle are addressing separate questions. Descartes sees final causality in terms of God’s ultimate ends of the universe which he thinks is an impossible question to answer. On the other hand, Aristotle is not really interested in the theological implications of natural or human causation (at least in the same way Descartes is), and is more interested in making an observable ontological claim that changeable things are directed to serve a good end. Humans seem to act with some good in mind (even if their “good” is misplaced). These are two separate and independent positions for each of these philosophers. Descartes, due to his quest for indubitable certainty, reduces final cause to efficient cause. Again, because he says, “The arguments…on behalf of final causality are to be referred to the efficient cause; thus it is open to us, from beholding the uses of the various parts in plants and animals to regard with admiration the God who brings these into existence” (441).

For Descartes, all we can really know about change and causation in the physical world is the efficient cause—that which influences or brings physical matter into some discernable form, and in this case, God is the efficient cause of all being—the best we can do is admire God who creates things into existence. Descartes’ epistemological skepticism keeps him from making any claim about purpose or goal-directedness in the physical world. In general, Descartes restricts his philosophical speculations to what he knows for certain, and usually applies formal and essential causation to God and the things of this world. For example he explains, “…I have at all points compared the formal cause or reason derived from God’s essential nature, which explains why he Himself does not need any cause in order to exist, with the efficient cause, without which finite things cannot exist” (384). For Descartes, God is the efficient cause of all things and anything beyond that, he seems to indicate, is not possible to speak of with strict precision and certainty. Therefore, he is unable to express ideas of what it means to live deliberately, be ethical, and order society for good. Descartes may not even deny that human actions are ordered to a good, but he leaves these types of questions regarding action, purpose, and agency untouched. At best, Descartes leaves these types of practical questions to the efficient cause of God.

Works Cited

Aristotle. The Works of Aristotle: 1 and 2. Great Books of the Western World. Vol. 7, 8. Encyclopedia Britannica, Inc., 1999.

Descartes, Rene. Bacon, Descartes, Spinoza.Great Books of the Western World. Vol. 28. Encyclopedia Britannica,Inc., 1999.