Arguments are of three kinds, Deduction, Induction, and what I call Abduction [—] If the conclusion is adopted, simply because it suggests itself as a possible fact which, if true, would necessitate ascertained facts, the Argument is Abductive. [—] It will be remarked that in the case of Abduction the only way in which the facts presented in the argument are any sign of the fact inferred is that they are an Icon […] of it.
From early/discarded draft
http://www.commens.org/dictionary/entry/quote-minute-logic-chapter-i-intended-characters-treatise-35