EXTREMES, in Logic, denote the two extreme terms of the conclusion of a syllogism; viz. the predicate and subject. They are called extremes, from their relation to another term, which is a medium or mean between them. The predicate, as being likewise had in the first proposition, is called the major extremum, greater extreme; and the subject, as being put in the second or minor proposition, is called the minor extremum, lesser extreme. Thus, in the syllogism, man is an animal; Peter is a man, therefore Peter is an animal; the word animal is the greater extreme, Peter the less extreme, and man the medium. See SYLLOGISM.
EXTREME and mean proportion, in Geometry, is when a line is so divided, that the whole line is to the greater segment, as that segment is to the other: Or, as it is expressed by Euclid, when the line is so divided, that the rectangle under the whole line, and the lesser segment, is equal to the square of the greater segment.