Free Why Darwin Matters by Michael Shermer

Sitters—those who have heard something about a claim or controversy and wonder what the explanation for it might be. Lacking a good explanation, the mind defaults to whatever explanation is on the table, regardless of how improbable it may be.
     
    Point four is particularly relevant to the debate between evolution and Intelligent Design. Before the theory of evolutionary biology was developed in the nineteenth century, the default explanation for the distribution of species around the globe was independent creation by God and the Noachian flood. (Among the handful of more religiously skeptical scientists, the mode of distribution was Lamarckian evolution and long-gone land bridges between continents and islands.) But after Charles Darwin and Alfred Russel Wallace demonstrated how natural selection changes varieties into different species when they migrate into different regions, the default supernatural explanation could be abandoned in favor of a fact-based natural one. Debate affords us an occasion to demonstrate to Fence Sitters that there is, in fact, a perfectly reasonable natural explanation for the apparently supernatural phenomenon of design. 2
Investigating Intelligent Design
     
    Skepticism—thoughtful inquiry—is a scientific way of thinking; science—a testable body of knowledge—is applied skepticism. At the core of any scientific investigation are a number of skeptical principles that help us assess the validity of a claim before we examine the specific arguments and evidences. Six principles of skepticism help us sort through the various arguments for Intelligent Design:
    Hume’s Maxim, or, what is more likely?
    In 1758 the Scottish philosopher David Hume published his most influential work,
An Enquiry Concerning Human Understanding
. When confronted by the claim of an event so improbable and extraordinary that it is called a miracle, Hume asks us to inquire what is more likely: that a supernatural act occurred contrary to the laws of nature, or that people who describe such acts are mistaken in their assessment of the event’s supernatural nature?
Hume’s Maxim
is best defined in his own words: “The plain consequence is (and it is a general maxim worthy of our attention),
‘That no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavours to establish.’
”
    Hume then weighs which is more likely: “When anyone tells me that he saw a dead man restored to life, I immediately consider with myself whether it be more probable, that this person should either deceive or be deceived, or that the fact, which he relates, should really have happened. I weigh the one miracle against the other; and according to the superiority, which I discover, I pronounce my decision, and always reject the greater miracle. If thefalsehood of his testimony would be more miraculous than the event which he relates; then, and not till then, can he pretend to command my belief or opinion.” 3
    The evolution–Intelligent Design debate boils down to a Humean question of what’s more likely: that the diversity and complexity of life we see around us came about by laws of nature that we can observe, or supernaturally by an Intelligent Designer that we cannot observe? The nineteenth-century social Darwinist Herbert Spencer answered the question rhetorically: “Well, which is the most rational theory about these ten millions of species? Is it most likely that there have been ten millions of special creations? or is it most likely that, by continual modifications due to change of circumstances, ten millions of varieties have been produced, as varieties are being produced still?” 4 It’s a good question.
    The Known and the Unknown, or, before you say something is out of this world, first make sure it is not in this world
.
    Creationists and Intelligent Design theorists explain natural phenomena by turning immediately to