As someone who supports Intelligent Design theory, I have often been puzzled by the many Catholic thinkers who do not.  The scientific basis for ID is strong, and ID is just as friendly to their theism as it is friendly to mine, so why do so many Catholic scholars reject ID, or at least have such strong reservations against it?  A recent essay by Edward Feser in Philosophia Christi[1] has enlightened me regarding the main source of contention between Catholic theology and ID theory, and it boils down to Aristotle, Thomas Aquinas, and final causation.

Feser explains that Thomists (those who follow the theological system of Thomas Aquinas, who followed the philosophy of Aristotle) believe teleology inheres within all substances (final cause) and is evident to rational minds, whereas ID theorists believe teleology must be imposed on substances from an external source (no final cause), and can only be detected empirically through various probability assessments (not evident).

Substances, Artifacts, and Final Causation: How ID Differs from Thomism

According to Aristotle and the medieval Scholastics, the universe contains a mix of substances and artifacts.  Substances possess a natural telos that inheres within the substance itself.  Aristotle identified this telos to which a substance naturally points as the “final cause,” meaning that for which something exists; i.e. its purpose or end-goal.  Artifacts have no inherent nature, and no telos.  The form/function of an artifact must be imposed on it from an external source (a mind/architect).

Modern science has rejected the Aristotelian notions of substance and final causation.  They see the universe as a conglomeration of artifacts operating mechanistically via the laws of nature, entirely void of teleology.  While the Intelligent Design movement accepts the existence of substances, they too reject final causation.  According to ID, both artifacts and substances have to have their teleology imposed on them by an external force since there is nothing that inheres within them capable of directing their telos to its natural end.

Aristotle posited four types of causes in the natural world:

1.      Material cause (that of which something is made)
2.      Formal cause (a thing’s essence, form, or pattern)
3.      Efficient cause (that which produces change)
4.      Final cause (that for which something exists)

The modern philosophy of science has eliminated both formal causes and final causes from the world.  It is believed that everything can be explained in terms of material and efficient causes.  ID theorists generally accept these same presuppositions, which is the source of conflict between Thomists[2] and ID theorists.  Thomists would contend that in eliminating final causation from the natural world, mainstream science and ID theorists have eliminated the foundation necessary to make sense of efficient causation.  Efficient causation presupposes final causation: A will produce B, rather than C,D, or E, only if producing B is the final cause (purpose) for which A acts.  Without final causation, there is no reason to think specific causes entail specific effects: A could produce B at time t1, C at time t2, D at time t3, or nothing at all at time t4.  Indeed, it was the rejection of final causation that opened the door to philosophers like David Hume to be skeptical of causation and induction altogether.  If there are no final causes, Hume reasoned that we cannot conclude that A causes B on induction alone.  Any effect is possible from any cause, and thus we must remain agnostic regarding questions of cause and effect.[3]

Because ID theorists reject final causation in the natural world, they assume teleology is absent unless and until it can be empirically detected.  Teleology can only be detected by calculating the probability of some natural substance X forming by chance.  If the probability is high that it could be formed by chance (because the complexity and specification of the substance are low), then there is no empirical reason to think teleology is present.  If the probability is low that it could be formed by chance (because the complexity and specification of the substance are high), however, then they conclude its origin is best explained by an external mind.  But on an Aristotelian view, probability and complexity have nothing to do with the detection of teleology.  Teleology is inherent within all substances.  There is no need to reason to teleology on the basis of an analogy to human designers, nor is there a need to suppose there is a grand designer in the first place.  Teleology can be detected wherever and whenever something is naturally directed toward a particular end, because it is in its nature to be that way (no outside mover is required).  We can recognize the nature and purpose of a substance even if we don’t its origin.  How to explain the presence of teleology is a different story.

The Fifth Way

For Aristotle there is no connection between teleology and theism.  He believed in a supreme deity (the Unmoved Mover), but on the basis of motion and change, not the presence of teleology in nature.  He viewed teleology as a brute fact about nature.  It’s just the way it is!  No mind is required to direct the process, and no further explanation is necessary.  The Scholastics accepted Aristotle’s view of final causes inhering within substances as part of their nature, but disagreed that teleology is a brute fact that needs no explanation.  They insisted that an explanation was necessary, and that explanation could be found in the divine intellect.  This was Aquinas’ argument in his Fifth Way.  He attempted to prove that an ordering intelligence is necessary to explain the teleology inherent within natural substances.  Aquinas writes:

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.

In other words, regularity implies teleology.  Aquinas is not appealing to probability, or pointing only to particular substances that exhibit a high degree of specified complexity.  He is speaking of all substances, which would even include those that lack a high degree of specified complexity.  At this stage of the argument, Aquinas is just regurgitating Aristotle.  The next stage of the argument is where he makes the connection to God:

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, whatever lacks intelligence can only be directed to its telos by something that has intelligence.  Mind is necessary to explain not just the presence of telos in substances, but how that telos is realized.

Aquinas is not basing his argument on probably, induction, analogy, or even an inference to the best explanation.  Instead, he’s arguing that unintelligent objects cannot move toward their telos unless they are directed by an intelligent agent.  He is making a metaphysical argument, not an empirical argument.  That’s what makes Aquinas’ Fifth Way different from the form of arguments presented by Paley and the ID movement, and why Thomism and ID tend to avoid each other at family reunions.

One argument raised against final causation is that it would mean a thing must exert causal influence before it even exists.  For example, the final cause of an acorn is an oak tree.  But how can an oak tree cause its own development if it does not exist until the development is complete?  This problem is avoided for intelligent minds.  For example, the form of a house is the formal cause of a house.  It is able to exert causal influence throughout the process because it exists in the mind of the builder from start to finish, guiding the development of the house to its telos.  In the case of non-conscious entities, however, they possess no mind in which the formal cause could exist to exert causal influence.  How, then, do they reach their telos?  The Scholastics argued that the final causes of non-conscious entities must exist as a form or idea in the mind of a transcendent being who directs these entities to their natural ends.  In essence, they argued as follows:

(1)  There is an irreducible teleology immanent within the natural order
(2)  This teleology is only intelligible if there is a transcendent intelligence to direct it
(3)  Therefore, there is a transcendent intelligence.

Since natural substances continue to realize their telos, the intelligence must continue to exert its causal influence in the world.  So not only does the Fifth Way give us a divine being, but it gives us a being who sustains and conserves the natural world.  Deism is ruled out.

[1]Edward Feser, “Teleology: A Shopper’s Guide” Philosophia Christi, Vol. 12 Number 1, 2010, pp. 142-159.
Clearly not all Catholics object to ID theory.  Indeed, some of the leading ID theorists are Catholic (e.g. Michael Behe).  The disagreement is more specifically between Thomists and ID theorists because Thomists adopt an Aristotelian view of the world that is not entirely consistent with the presuppositions of ID theory.
Hume settled for mere correlations between A and B instead.