The Definition for Biological Evolution

For some time now, believers in evolution have been goading me to define biological evolution, and comment on "the scientific method." I haven't, for a good reason.

Talk Origins says this about the definition of "evolution":

"Unfortunately the common definitions of evolution outside of the scientific community are different. For example, in the Oxford Concise Science Dictionary we find the following definition:

"Evolution: The gradual process by which the present diversity of plant and animal ...