Editing Abductive reasoning (section)

=====Classification of signs=====
As early as 1866,<ref>Peirce, C. S., the 1866 Lowell Lectures on the Logic of Science, ''[[Charles Sanders Peirce bibliography#W|Writings of Charles S. Peirce]]'' v. 1, p. 485. See under "[http://www.helsinki.fi/science/commens/terms/hypothesis.html Hypothesis]" at ''Commens Dictionary of Peirce's Terms''.</ref> Peirce held that:

1. Hypothesis (abductive inference) is inference through an ''icon'' (also called a ''likeness''). <br />
2. Induction is inference through an ''index'' (a sign by factual connection); a sample is an index of the totality from which it is drawn. <br />
3. Deduction is inference through a ''symbol'' (a sign by interpretive habit irrespective of resemblance or connection to its object).

In 1902, Peirce wrote that, in abduction: "It is recognized that the phenomena are ''like'', i.e. constitute an Icon of, a replica of a general conception, or Symbol."<ref>Peirce, C. S., "A Syllabus of Certain Topics of Logic", written 1903. See ''[[Charles Sanders Peirce bibliography#EP|The Essential Peirce]]'' v. 2, p. 287. Quote viewable under "[http://www.helsinki.fi/science/commens/terms/abduction.html Abduction]" at ''Commens Dictionary of Peirce's Terms''.</ref>