Tag Archives: Deduction

The Design Analogy

The DNA Structure – Illustration by Zephyris – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15027555

There is a theory, known as Intelligent Design (ID), that postulates that “certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection.”[1] Many people reject this theory out of hand, and yet it just won’t go away. Why is ID so persistent? I would suggest it’s because analogy is so powerful. We tend to think analogically. We use analogies to work through difficult problems. When we have difficulty understanding a concept, a common first move is to try to find some way the new concept is analogous to something we already understand. Of course, all analogies break down at some point. Otherwise the 2 things being compared would be fully identical. But analogies help us to correlate known causes or effects with newly observed ones. Think back to when you had trouble understanding something new, and a friend or mentor who knew you well enough to know what kind of concepts you understood well, said “It’s like this…” and related it to something you were familiar with, and it suddenly clicked.

The problem for the atheist seeking a materialistic explanation for the universe and the existence of intelligent life is that we can’t seem to avoid analogies – comparisons – to design. Intelligent Design is such a persistent idea because so much of nature is analogous to human design. It’s actually pretty difficult to describe many things in nature without using design-centric terminology: we commonly speak of the “genetic code” and the “blueprints” of DNA; different “body plans” of the each species; the fine-tuning of the universe with its “clockwork precision”; cellular “pumps” and “motors”, and the “wiring” of our nervous system; and the “purpose” of different natural components. Even Richard Dawkins defined biology as “the study of complicated things that give the appearance of having been designed for a purpose” and speaks of our bodies as consisting of trillions of cells “organized with intricate architecture and precision engineering into a working machine….”[2]  In fact, the human body has been compared to a “system of systems” similar to a building’s structural skeleton, architectural skin and functionality, and mechanical ventilation, plumbing, and electrical systems, except far more complex than anything any human has ever designed. The analogies between what we see in nature and the results of the human design process really do seem to flow rather readily, don’t they? Of course, the bacterial flagellum has become the poster-child for intelligent design, but why not? The analogy between it and an electric motor, both in function and even in individual parts really is uncanny. When searching for descriptions for natural processes and their results, all of these design-related terms keep rising to the surface as the most appropriate, fitting, terms to use. Why is that?

To answer why this whole debate between Intelligent Design and Naturalism even arises, let’s look at the what analogy really is. Peter Kreeft addresses this topic in his Socratic Logic textbook, where he makes several relevant points.

  • Analogies are often not meant as arguments to prove a case, but simply illustrations to better explain some part of it.
  • Arguments based on analogy do not prove anything with certainty, only varying degrees of probability.
  • Arguments from analogy are the most common kind of inductive argument and actually make up most of our daily inferences.
  • “Argument by analogy is an really an abbreviated form of induction and deduction together.”[3]

Now, I would say that ID isn’t simply attempting to make an illustration, but a proper argument, so let’s lay out some terms first. Induction is (typically) the process of drawing general conclusions based on observation of specific instances. The most basic form of induction is induction by simple enumeration. Think of statistics; you measure a certain part of a test population and induce some general conclusion from the sample you measured. The more you measure the more certain your conclusion. But generally, you cannot be certain except in the case that you measure every possible instance. Deduction is (typically) the process of reasoning that applies general principles to specific instances. Provided the premises are true and the conclusion logically follows from the premises, a deductive argument will provide certainty.

Now analogy is said to be a combination of the two because when we draw an analogy, we are thinking of multiple past instances of something, inferring a general conclusion from that previous track record, recognizing (perhaps unconsciously) the common essence tying those past instances together, as well as that common essence in a new instance, and applying that general principle to the new instance. Analogies provide us a shortcut for that thought process. The more cases we’ve seen, the more similarities between those cases and the new one under investigation and the more relevant they are, and the fewer the dissimilarities between them,  the more certainty we can have that the analogy is sound.

So why won’t Intelligent Design go away? Perhaps because we can recognize an intelligent mind behind all of our human designs, can infer that a mind is what’s required to generate any design, can recognize the twin pillars of design – choice and purpose – in many natural objects and processes we observe, and can therefore reasonably apply that concept of design to them even if we haven’t figured out the identity of the Designer yet. Of course, ID is just a scientific theory, and stops short of identifying the Designer, but we can apply what we know about the necessary attributes of this mystery guest to arrive at an identity. The question for my skeptical friends is this: if the evidence points to nature being the result of design, and the omniscient, omnipotent, omnipresent, ontologically necessary, free agent known as God in the Bible is the best fit for the source of that design, will you follow the evidence where it leads?


[1] “Intelligent Design”, New World Encyclopedia. http://www.newworldencyclopedia.org/entry/Intelligent_design, accessed 2017-02-15.
[2] Both quotes are from Chapter 1 of Dawkins’ 1986 book The Blind Watchmaker.
[3] Peter Kreeft, Socratic Logic (South Bend: St Augustine’s Press, 2010), pp.329-31.

Building Arguments, Houses, and the Universe

Home ConstructionA while back, we looked at the Teleological Argument (the argument for the existence of God from the design observed in the natural world). You can click here to review that, but today I want to unpack a one-sentence version of this case presented in the Bible. Yes, one sentence. But first, we need some background on different ways of building logical arguments. Typically, these are put forward as a deductive argument called a syllogism: two premises and a conclusion that should necessarily follow from the premises. If it does, and the terms in the premises are unambiguous, and the premises are true, the conclusion must be true. Here’s a common version of the design argument in syllogistic form:

  1. Every design has a designer. (Major Premise)
  2. The universe was designed. (Minor Premise)
  3. Therefore, the universe had a designer. (Conclusion)

The typical design argument described above is called a deductive argument. Deduction uses the essential nature of something  to state a universal proposition and apply that with certainty to a particular case. The major premise that every design has a designer is the universal statement in the syllogism above. That is just part of the nature of design, so that will also apply to any particular object exhibiting design, even if that object is the entire universe. Because an essential characteristic applies to all members of a set, well-formed deductive arguments provide us with certainty about the conclusion. But deduction typically arrives at these universal propositions on the basis of a prior induction.[1] What’s that? Glad you asked…

Inductive arguments typically use sense perception to examine particular instances of a set of specimens and infer a general characteristic about the set. However, the inductive argument’s dependence on observing particulars means that its conclusion is never certain until we understand the essence common to all the particulars that explains why the conclusion must be so. Without that additional step of reasoning, the inductive conclusion can never be certain, only probable. [2]

Typically (for better or worse), we don’t take the time to organize our thoughts into formal inductive or deductive arguments. We take shortcuts. One very common shortcut is called argument by analogy. This is actually the most common form of inductive argument as everyone draws analogies at some point. Analogies actually combine four steps into one. That’s OK as long as the reasoning behind the shortcut is still valid. I came across a verse in the Bible that uses the analogy shortcut to condense the teleological argument into one sentence. Hebrews 3:4 tells us that “every house is built by someone, but the builder of all things is God.” Let’s walk through the four steps together.[3]

  1.  Observation. The author observes that every particular instance of a house is the result of a builder.
  2. Induction. The author infers the universal principle that all houses require a builder.
  3. Understanding. The author understands why the universal principle is an essential and necessary part of the instances observed rather than just a coincidence. Anything which is built entails selection and assembly of parts by an agent so as to achieve an end-goal. That agent is the builder.
  4. Deduction. The author deduces an application to another instance from this universal principle. In this case, the principle of a required builder (agency), applies to “all things”, for we recognize assembly, and contingency, and purpose  – the signature of a builder – everywhere we look.

As in the modern teleological argument, it does not explicitly follow that God is the builder, but the author of Hebrews includes that credit in the conclusion based on the attributes of God that make Him the only possible option. While omnipotence and omniscience would be virtually required to build all things, it’s His immateriality and eternality that really make God the only logical possibility. These are the two attributes that would allow a potential builder to exist prior to the existence of space and time. For instance, even if a super-powerful, super-smart alien had the ability to design and construct a universe, as a material being, it would still require the existence of space in order to itself exist. Suppose that same alien were a truly immaterial, but non-eternal,  “ghost”. That might get around the dependence on space, but as best as we can determine scientifically, the universe had a definite beginning where space and time both came into existence together. Whatever begins to exist has a cause, and any potential designer constrained by time would therefore have to have a beginning along with the universe supposedly being designed by it. Shortening that law of causality to “whatever exists has a cause” is responsible for the typical misunderstanding of atheists like Richard Dawkins when they ask “Who made God?” They’re trying to demonstrate an infinite regress of causes, but forget that causality is predicated on something having a beginning. Eternality stops the infinite regress of causal events by allowing a first uncaused cause. That attribute can only be possessed by a necessary being, and there can only exist one necessary being. Therefore, God has to be the “builder” (or “designer”).


[1] Peter Kreeft, Socratic Logic, Edition 3.1 (South Bend: St Augustine’s Press, 2010), p.314.
[2] One exception to this is the “complete induction”, where we have examined every member of a set, and can draw an inductive  conclusion with certainty without recognizing the common essence.
[3] ibid., p.329-331.