The ID concept affirms that living things are designed and exhibit irreducible complexity. Some examples are the biochemistry of vision and the mammalian blood-clotting pathway. These biological pathways consist of many factors, and all the factors are necessary for the pathway to function properly. Thus, evolution (which works via the mechanism of small, gradual steps that keep only that which is immediately functional) could not have formed these pathways.
For example, if only three of the blood-clotting factors (there are many factors in the complete pathway) were formed in an organism, blood would not clot, and thus the factors would not be kept because they are not currently useful to the organism. Evolutionary processes do not allow the organism to keep the three factors in the hopes that one day the rest of the blood-clotting factors will form.
Evolution is goalless and purposeless; therefore, it does not keep the leftovers. The question of whether a feature of a living organism displays design can be answered by using what is called an explanatory filter.
The filter has three levels of explanation:
1. Necessity — did it have to happen?
2. Chance — did it happen by accident?
3. Design — did an intelligent agent cause it to happen?
This is a very logical, common-sense approach used by individuals every day to deduce cause and effect. For example, consider the scenario of a woman falling:
1. Did she have to fall? No, but she did.
2. Was it an accident?
3. Or was she pushed?
If we apply this explanatory filter to living organisms, a feature must be designed if the first two answers are no. Let us evaluate the blood-clotting pathway with respect to these three questions:
1. The blood-clotting pathway is compatible with, but not required by, the natural laws of biology and chemistry; so it is not a necessity specified by natural phenomena.
2. It is complex because it is composed of many factors, thus the remote probability that it happened by chance. (Note that complex structures fall into two categories: ordered complexity and specified complexity. A snowflake, although complex structurally, has little information and thus is considered an example of ordered complexity. It is the direct result of natural phenomena rather than intelligent design).
3. The blood-clotting pathway does show design, referred to as specified complexity because it is complex and has a high amount of information. It is the direct result of an intelligent agent. All the factors must be present and interact with each other in a specified manner in order for the pathway to be functional.
Thus, the blood-clotting pathway meets all the requirements for irreducible complexity, and so must be designed.1
“For you formed my inward parts; you knitted me together in my mother’s womb. I praise you, for I am fearfully and wonderfully made.”Psalm 139:13-14
References and Notes
- Ham, Ken. The New Answers Book 2 . Master Books. Kindle Edition.