Aquinas’ fifth way is a teleological argument. It is a proof from the final causes of the things around us.
Aquinas states the argument thus:
“The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.”
In other words, the adaptation of means to ends is evidence and sign of an intelligent cause. The universe provides us on every side with examples of the adaptation of means to ends. It follows logically then that the universe is the work of an intelligent cause.
Before we more fully explicate this argument, let’s define some terms and clarify some concepts. A cause is termed a “means” to a particular result when its action has been determined in view of that result as an end. Works of humans are as a rule means. A bit in the horse’s mouth is a means of control. The use of a knife is a means of carving wood. The automobile is a means of transporting people and materials.
But means are not limited to only rational actors. Means are anything that serve as efficient causes. As Aquinas sums it up: “Every agent acts for an end: otherwise one thing would not follow more than another from the action of the agent, unless it were by chance” (Summa Theologiae I.44.4).
For example, an ice cube floating in a glass of water causes the water to grow colder. The ice cube is an agent that if unimpeded will cause the water to grow colder. It will not cause the water to change into iced tea, boil, catch fire, or have no effect at all. In the natural order of things, we expect that placing an ice cube in a glass of water will cool the water because that is the usual and normal effect. There is in ice a potency, power, or disposition that inherently indicates or points to the generation of this specific effect. The ice cube is an efficient cause of coldness. The generation of the coldness of the water is the final cause of the ice.
To state in general terms. If there is a regular efficient causal connection between a cause A (ice cube) and an effect B (the coldness of the water), then generating B is the final cause of A in the sense that A inherently “points to” B or is “directed at” B as its natural effect.
Examples of such final causation abound in the natural environment. The regularity of the moon orbiting the earth is such a one. The moon just doesn’t orbit the earth in a general regularity; it orbits the earth specifically rather than swinging widely out to Venus or Mars or rather than stopping suddenly for 3 days and then resuming its path. No the moon’s orbit is so regular that we can use it to mark time. An acorn will always give rise to an oak tree. Acorns don’t regularly give rise to peach trees or monkeys. The acorn then is inherently directed to become an oak tree as its natural end.
In fact, such regularity, such predictability is a hallmark of the universe – and is exploited by modern science in man’s search for understanding the physical laws of nature. In each such case, efficient causes don’t just happen to produce specific results. The efficient cause, e.g, the ice floating in the glass of water, is inherently directed toward certain specific effects as if towards a “goal”. If I want an oak tree in my front yard, I would plant an acorn not a walnut. If I want a nice cold drink of water, I put ice in my glass.
It doesn’t matter if such cause-effect relationships are consciously based or not. Goal-directedness, i.e., final causation, can and does exist in the natural world apart from conscious awareness. Ice results cool the water whether or not a conscious being placed the ice in the water or not. The moon will regularly orbit the earth even if no one ever noticed or studied the motion. An acorn falling to the ground in a remote forest will still give rise to an oak tree – even if no one ever enjoys its shade.
But, critics say, in order for something to act as a cause, it must exist. How can something exert an effect, be a final cause, even before it exists. To say that an oak tree is the final cause of an acorn suggests that somehow the oak tree exerts influence on the acorn to go through all the various stages of its development even before the oak tree actually exists.
For a cause to be efficacious – including a final cause – it has actually to exist in some way. It’s not just that for A to be the efficient cause of B, A must exist – as it obviously must – but also that for B to be the final cause of A, B must also exist, in some sense. Otherwise, being nonexistent, it could not be efficacious. Hence for the “coldness” that the ice generates to function as a final cause, it has to exist in some way; for an oak tree to function as the final cause of an acorn, it too has to exist in some way; and so forth.
Now as we have already explored, there are two ways for something to exist. A thing may exist in the natural world, or a thing may exist in an intellect. Oak trees do exist in the natural world. However right now as I write this in my office, I am thinking of an oak tree. The oak tree that I am holding in mind has existence, although its existence is different from the oak tree outside my window.
What does this have to do with the whole notion of final causes? Perhaps another example will help.
Think of a carpenter who decides to design and build a chair. The design of the chair does not exist in the natural world. The design is something held in the intellect of the carpenter. The carpenter is the cause of certain effects – the shaping and construction of the materials. But the reason he is able to do this is that the effect, the chair, exists as an idea in his intellect before it exists in reality. This is how the idea of the chair can serve as a final cause – by means of its form or essence in the carpenter’s intellect, if not yet in the natural world. And as mentioned above and elsewhere in this blog, this is the only way something not yet existent in the natural world can exist in any sense at all, and thus, have any effects at all: that is, if it exists in an intellect.
Now let’s consider the enormous number of causes that constitute the natural universe. Every one of them is directed toward a certain end or final cause. The acorn is directed to grow into an oak tree. The ice is directed to cooling down the water. But, it would seem, that almost all of the causes in the universe are not associated with any consciousness, thought, or intellect at all. Even animals and humans, who are conscious, are themselves comprised in whole or part of unconscious and unintelligent material components which themselves exhibit final causality, undergo changes directed to regular, predictable effects (final causes).
But as we have seen, final causes must have existence in some sense in order to be efficacious. It they do not have existence in the natural world, then the only place left for them to exist is in an intellect, and this intellect must exist outside the natural order altogether. For the causal relations in question are totally unintelligent: ice and acorns do not have intellects, nor is there any intelligence at the level of the even more fundamental causal processes studied by basic physics and chemistry. And all the intelligence that does exist within the material world – in us, for example – presupposes the operation of these unintelligent causal processes (since the existence of our bodies, and thus of us, presupposes them). So, there is no place left for the intellect in question to be than outside the natural order. That is to say, all the causal relations that exist in the natural order exist at all only because there is an intellect outside the natural order which “directs” causes to their effects.
This argument, you will notice, makes no mention of “intelligent design” nor does it hypothesize or try to explain the origins of the universe. Nor does the argument hinge on “irreducible complexity”. If all that existed was a single electron orbiting a single proton, the argument would still hold. The argument depends on the various causes here and now and which are directed to certain ends here and now. The argument is that such changes here and now could not exist at all apart from an intellect outside the natural order directing causes to effects. This includes any biological causes involved in evolution. The argument is a conceptual necessity. It is logically, conceptually impossible that there could be such final causation without a sustaining intellect.
Aquinas correctly equates this intelligence outside the natural order with God. It could not be otherwise. Whatever ultimately orders things to their ends must also be the ultimate cause of those things. Having an end is part of the nature or essence of a thing. For that nature or essence to be of something real, it must have existence. Whatever determines that a thing exists with a certain end is the same as that which conjoins its essence and existence. In other words, causes them to be.
As we have shown earlier, the ultimate or First Cause of things must be Being itself. Thus, this intelligence outside the natural order must be identical with the First Cause, with the Unmoved Mover, and with all the attributes we have shown to belong to God.
Thus, Aquinas is able to say simply, “Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God”.
