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since 11.15.04


Scientific Reasoning

Department of History and Philosophy
Learning Center M33
Lander University
Greenwood, SC 29649

Analogical Arguments

  1. An analogy is a relationship between two or more entities which are similar in one or more respects. An analogy is present whenever the following descriptions are present: resemblance, similarity, correspondence, likeness, comparison, similitude, counterpart, image, resemblance of relations and mapping.

    1. Some of the nonargumentative uses of analogy include cases in literature and explanation.

      1. Literary analogies produce a vivid impression in the reader's mind.

        1. Metaphor is a figure of speech in which a word or phrase literally denoting one kind of object or idea is used in place of another to suggest a likeness or analogy between them (without the use of "like" or "as").

          1. E.g., the ship plows the sea.
          2. E.g., computers have senses and a memory.
          3. E.g., his fist was a knotty hammer

        2. Similié is a figure of speech comparing two unlike things often introduced by the words, "like" or "as."

          1. E.g., cheeks like roses.
          2. E.g., "And ice mast high came floating by
            As green as emerald."
          3. "Mary Lou Wingate as slightly made
            And as hard to break as a rapier blade."<

      2. An analogical explanation makes something unfamiliar understandable by comparing to something more familiar.

        1. The atom is (like) a miniature solar system.
        2. A tree is (like) a factory.
        3. The plum pudding model of the atom is one of electrons surrounded by a "pudding" of positive charges.

    2. Scientific reasoning involves the argumentative uses of analogy.

      1. An analogical inference is drawn from a resemblance of relations.

        1. J. S. Mill's example of a country which has sent out colonies is termed "the mother country."
        2. The colonies stand in the same relation to her as parents do to their children
        3. Reasoning by analogy, then, obedience or affection is due by the colonies to the mother country.

          parents → children
          mother country → colonies

      2. An analogical inference proceeds from the similarity of two or more things in one or more respects to the similarity of those things in some further respect. (In point of fact, this definition is true of any inductive argument.)

        1. The difference between an analogical inference and the case of a "complete induction" is that there is an invariable connection between the respects mentioned (c.f., P, Q, R, below). Thus, in the case of a "complete induction," Mill's Method of Agreement and Difference cannot be used.

        2. Even so, these respect must not b known to be unconnected to each other, for, in this case, the argument would have no plausibility.

        3. Hence, no antecedent evidence for a connection in an analogical inference can be assumed. The analogy is a guidepost for more rigorous investigation or can be used when subject is out of reach of further observation and experiment.

        4. The general form of an analogical argument is as follows, where a, b, c, d stand for entities, and P, Q, R stand for respects,

          • a, b, c, d all have the attributes P and Q.

          • a, b, c all have the further attribute R. [data base]
          • _______________________________

          • Thus, d probably has the attribute R.

        5. An analogical inference can be a rigorous induction if the respects or circumstances of resemblance are the material or fundamental circumstance* on which all the consequences necessary to be taken into account depend. (An ultimate property is one that is not a consequence of other properties. If the resemblance is an ultimate property, there will be resemblance in the derivative properties.)

        6. Consequently, analogical arguments can vary in rigor from accidental to deductive.

  2. One possible extension of the theory of analogy is to extend the kinds of analogies to other cases. (Note the relevance to classificatory sciences.)

    1. Analogies of Similarity, as in the general form of an analogical argument.

    2. Analogies of Diversity, where there is an absence of respects.

    3. Conflicting Analogies are like Wittgenstein's notion of a family relation. These analogies are different in some circumstances and similar in others.

      1. E.g., paintings can be compared to the styles of different masters.

      2. A vase can have Etruscan, Grecian, and Egyptian respects.

    4. Consider the following example:

      • Smith, Jones, Wilson, and Johnson have whitish lips, pale complexions, and whitish fingernails.

      • Smith, Jones, and Wilson have low blood iron levels.
      • ________________________________

      • Johnson probably has a low blood iron level.



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