A common criticism of Intelligent Design (ID) is that it represents an “argument from ignorance.” According to this objection, ID advocates reason that because science has not yet explained how biological information arose through natural processes, an intelligent cause must therefore be responsible.
An argument of that kind would indeed be logically inadequate:
Premise: We do not know how natural processes produced biological information.
Conclusion: Therefore, intelligence produced it.
However, proponents of Intelligent Design argue that this does not accurately represent their reasoning. Instead, they present the design argument as an inference to the best explanation based on both negative and positive evidence.
Negative and Positive Evidence
The argument has two components.
First, proponents argue that known undirected material mechanisms have not demonstrated the capacity to generate the large amounts of functionally specified information required for the origin of the first living systems.
Second, they appeal to what they regard as positive causal evidence: from ordinary experience, intelligent agents are known to produce information-rich systems, including written language, computer software, mathematical codes, and engineered systems.
The argument can therefore be summarized:
Premise 1: After investigation, proposed undirected material causes have not demonstrated the ability to produce the relevant kind and quantity of specified information.
Premise 2: Intelligent agents are known to produce information-rich, functionally specified systems.
Conclusion: Intelligent agency should therefore be considered as a candidate—and, according to ID proponents, the best available explanation—for the origin of specified biological information.
Inference to the Best Explanation
This distinction is important. An argument from ignorance concludes that one explanation must be correct merely because another explanation has failed.
An inference to the best explanation, by contrast, compares competing explanations and asks which known type of cause has the demonstrated causal capacity to produce the phenomenon being investigated.
This form of reasoning is common in the historical sciences. Geologists, archaeologists, paleontologists, and other historical scientists investigate events they cannot directly observe by comparing present evidence with known cause-and-effect relationships.
This approach is sometimes summarized by the uniformitarian principle:
“The present is the key to the past.”
Present knowledge of what different causes are capable of producing is used to evaluate competing explanations for events in the past.
The ID Argument in Logical Form
The distinction can be expressed simply:
Argument from ignorance
Cause X has not explained evidence E.
Therefore, cause Y produced E.
Inference to the best explanation
Causes A–X have not demonstrated the capacity to produce evidence E.
Cause Y is independently known to produce E.
Therefore, Y may provide a better causal explanation of E than A–X.
The crucial difference is the second premise. The inference to design is not intended to rest solely on what material processes allegedly cannot accomplish. It also appeals to what intelligent causes are independently known to accomplish.
The Central Question
The debate therefore should not end with the statement:
“Science does not yet know how biological information originated.”
The more substantive scientific and philosophical question is:
**Which proposed cause has demonstrated the greatest causal adequacy to explain the origin of functionally specified biological information?**
For proponents of Intelligent Design, it is this combination of evaluating competing explanations and appealing to the known causal power of intelligence that distinguishes the design inference from an argument from ignorance.
Whether one ultimately accepts that conclusion depends on how one evaluates the relevant evidence and competing explanations. But the argument itself is intended to be a positive inference about causal adequacy, rather than simply an appeal to what is currently unknown.
