Signs of Intelligence
A Primer on the Discernment of Intelligent Design
by William A. Dembski
Intelligent design examines the distinction between three modes of explanation: necessity, chance, and design. In our workaday lives we find it important to distinguish between these modes of explanation. Did she fall or was she pushed? And if she fell, was it simply bad luck or was her fall unavoidable? More generally, given an event, object, or structure, we want to know:
1. Did it have to happen?
2. Did it happen by accident?
3. Did an intelligent agent cause it to happen?
Given an event to be explained, the first thing to determine is whether it had to happen. If so, the event is necessary. By “necessary” I don’t just mean logically necessary, as in true across all possible worlds, but I also include physical necessity, as in a law-like relation between antecedent circumstances and consequent events. Not all events are necessary.
Events that happen but do not have to happen are said to be contingent. In our workaday lives we distinguish two types of contingency, one blind, the other directed. A blind contingency lacks a superintending intelligence and is usually characterized by probabilities. Blind contingency is another name for chance. A directed contingency, on the other hand, is the result of a superintending intelligence. Directed contingency is another name for design.
An Ancient Question
This characterization of necessity, chance, and design is pretheoretical and therefore inadequate for building a precise scientific theory of design. We therefore need to inquire whether there is a principled way to distinguish these modes of explanation. Philosophers and scientists have disagreed not only about how to distinguish these modes of explanation, but also about their very legitimacy. The Epicureans, for instance, gave pride of place to chance. The Stoics, on the other hand, emphasized necessity and design, but rejected chance. In the Middle Ages Moses Maimonides contended with the Islamic interpreters of Aristotle who viewed the heavens as, in Maimonides’s words, “the necessary result of natural laws.” Where the Islamic philosophers saw necessity, Maimonides saw design.
In arguing for design in his Guide for the Perplexed, Maimonides looked to the irregular distribution of stars in the heavens. For him that irregularity demonstrated contingency. But was that contingency the result of chance or design? Neither Maimonides nor the Islamic interpreters of Aristotle had any use for Epicurus and his views on chance. For them chance could never be fundamental but was at best a placeholder for ignorance. Thus for Maimonides and his Islamic colleagues the question was whether a principled distinction could be drawn between necessity and design. Maimonides, arguing from observed contingency in nature, said yes. The Islamic philosophers, intent on keeping Aristotle pure of theology, said no.
A Modern Demise
Modern science has also struggled with how to distinguish between necessity, chance, and design. Newtonian mechanics, construed as a set of deterministic physical laws, seemed only to permit necessity. Nonetheless, in the General Scholium to his Principia, Newton claimed that the stability of the planetary system depended not only on the regular action of the universal law of gravitation, but also on the precise initial positioning of the planets and comets in relation to the sun. As he explained:
William A. Dembski is Associate Research Professor in the Conceptual Foundations of Science at Baylor University and a senior fellow with the Discovery Institute?s Center for Science and Culture. He is the author of many books, including Intelligent Design (InterVarsity Press), No Free Lunch (Rowman & Littlefield), and The Design Revolution (InterVarsity Press); and the editor, with James Kushiner, of Signs of Intelligence (Brazos), a collection taken from the first Touchstone special issue on intelligent design.
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