induction

—inductionless, adj.

/in duk"sheuhn/, n.

1. the act of inducing, bringing about, or causing: induction of the hypnotic state.

2. the act of inducting; introduction; initiation.

3. formal installation in an office, benefice, or the like.

4. Logic.

a. any form of reasoning in which the conclusion, though supported by the premises, does not follow from them necessarily.

b. the process of estimating the validity of observations of part of a class of facts as evidence for a proposition about the whole class.

c. a conclusion reached by this process.

5. Also called mathematical induction. Math. a method of proving a given property true for a set of numbers by proving it true for 1 and then true for an arbitrary positive integer by assuming the property true for all previous positive integers and applying the principle of mathematical induction.

6. a presentation or bringing forward, as of facts or evidence.

7. Elect., Magnetism. the process by which a body having electric or magnetic properties produces magnetism, an electric charge, or an electromotive force in a neighboring body without contact. Cf. electromagnetic induction, electrostatic induction.

8. Embryol. the process or principle by which one part of the embryo influences the differentiation of another part.

9. Biochem. the synthesis of an enzyme in response to an increased concentration of its substrate in the cell.

10. an introductory unit in literary work, esp. in an early play; prelude or scene independent of the main performance but related to it.

11. Archaic. a preface.

[1350-1400; ME induccio(u)n < L induction- (s. of inductio). See INDUCT, -ION]

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I

In logic, a type of nonvalid inference or argument in which the premises provide some reason for believing that the conclusion is true.

Typical forms of inductive argument include reasoning from a part to a whole, from the particular to the general, and from a sample to an entire population. Induction is traditionally contrasted with deduction. Many of the problems of inductive logic, including what is known as the problem of induction, have been treated in studies of the methodology of the natural sciences. See also John Stuart Mill; philosophy of science; scientific method.

II

(as used in expressions)

electromagnetic induction

electrostatic induction

induction problem of

induction heating

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▪ embryo

      in embryology, process by which the presence of one tissue influences the development of others. Certain tissues, especially in very young embryos, apparently have the potential to direct the differentiation of adjacent cells. Absence of the inducing tissue results in lack of or improper development of the induced tissue. The converse is often true as well; i.e., the addition of extra inducing tissue in an abnormal position in an embryo often results in aberrantly located induced tissue.

      An example of induction is the development of the eye (eye, human) lens from epidermis under influence of the eye cup, which grows toward the skin from the brain. As the eye cup comes into contact with any neighbouring epidermis, it transforms that particular region into a lens. The exact nature of the stimulus for lens induction is not known, although ribonucleic acid (RNA) has been implicated as a messenger.

      The range of the inductive effect is not unlimited, for only certain tissues are capable of being induced by a given structure and then only at certain times.

▪ enzymatic reactions

      in enzymology, a metabolic control mechanism with the effect of increasing the rate of synthesis of an enzyme. In induction, synthesis of a specific enzyme, called an inducible enzyme (e.g., β-galactosidase in Escherichia coli), occurs when cells are exposed to the substance (substrate) upon which the enzyme acts to form a product.

      Formation of β-galactosidase has been shown to be controlled by a so-called regulator gene presumed to specify a protein, called a repressor protein, that binds to the region of deoxyribonucleic acid ( DNA) responsible for directing the synthesis of the enzyme. If substrate is present, it acts as an inducer by combining with the repressor so as to prevent its binding to DNA. As a result, the enzyme is synthesized; i.e., its formation by the microorganism is induced.

      Such mechanisms are important in the cell because they prevent the synthesis of enzymes that a cell cannot use; e.g., β-galactosidase is needed only when its substrate (lactose or galactose) is present.

▪ reason

      in logic, method of reasoning from a part to a whole, from particulars to generals, or from the individual to the universal. As it applies to logic in systems of the 20th century, the term is obsolete. Traditionally, logicians distinguished between deductive logic (inference in which the conclusion follows necessarily from the premise, or drawing new propositions out of premises in which they lie latent) and inductive logic, but the problems earlier subsumed under induction are considered to be concerns of the methodology of the natural sciences, and logic is generally taken to mean deductive logic.

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