Is Intelligent Design a Circular Argument?

Recently we received an e-mail from a reader asking if ID is a "circular argument." He described ID like this:

Complex stuff doesn't just arise spontaneously, it can only arise through ID. Therefore, if we find evidence of complex stuff, that serves as proof it was ID-ed.

In a very rough and rudimentary kind of way, this is not a totally inaccurate description of the basic case for intelligent design. However, it is not a circular argument.

ID is a historical science based upon the principle of...