Allen MacNeill

Arguments by analogy are common in science, and in pseudoscience as well (especially "intelligent design theory"). A hierarchy of reasoning modes is presented, in which increasing confidence in the validity of inferences arises out of increasing lines of related evidence. The validity of all forms of argument are shown to be limited by the same thing: the logical limitations of argument by analogy. Therefore, there is (and can be) no ultimate certainty in any description or analysis of nature insofar as such descriptions or analyses are based on transduction, induction, deduction, abduction, and/or consilience (TIDAC). Generalizations formulated via simple analogy (transduction) are the weakest and generalizations formulated via consilience are the strongest. All we have (and can ever have) is relative degrees of confidence, based on repeated observations of similar objects and processes.