The earliest (and most-discussed) theory of generative metrics is that put forth by
Morris Halle and
Samuel Jay Keyser — first in 1966 with respect to Chaucer's iambic pentameter, and in its full and revised form in 1971's
English Stress: Its Forms, Its Growth, and Its Role in Verse. Halle and Keyser conceive of the iambic pentameter line as a series of (nominally) 10 Weak and Strong positions: W S W S W S W S W S but to accommodate
acephalous lines, and feminine and triple endings, use this full formulation: (W) S W S W S W S W S (x) (x) where the first Weak position is optional, and the final 2 positions (which
must be unstressed) are also optional. They then define their signal concept, the
Stress Maximum, as a stressed syllable "located between two unstressed syllables in the same syntactic constituent within a line of verse". Finally, the fit between syllables and the positions they occupy are evaluated by these 2 hierarchical sets of
correspondence rules: (i) A position (S or W) corresponds to either :1) a single syllable, :or :2) a sonorant sequence incorporating at most two vowels (immediately adjoining to one another, or separated by a
sonorant consonant). AND (ii) :1) Stressed syllables occur in S positions and in all S positions; :or :2) Stressed syllables occur only in S positions, but not necessarily in all S positions; :or :3) Stress Maxima occur only in S positions, but not necessarily in all S positions. Rules are evaluated in order. If rules (i)-1 or (ii)-1 or (ii)-2 are broken, this indicates increasing complexity of the line. But if (i)-2 or (ii)-3 are broken, the line is unmetrical. (Note that some sources erroneously state that the presence of a Stress Maximum makes a line unmetrical; this is false. In Halle & Keyser's theory a Stress Maximum
in a W position makes a line unmetrical.) An example of Halle and Keyser's
scansion is: / / / M / many bards the ses of time! W S W S W S W S W S Stresses are indicated by a slash "/" and Stress Maxima by "M". A single underline indicates a violation of (ii)-1; a double underline indicates a violation of (ii)-1 & 2. In addition, the Stress Maximum "lap", since it occurs on a W position, violating (ii)-3, should get a third underline, rendering the line unmetrical. (Because of display limitations, this is here indicated by striking out the "M".) Joseph C. Beaver, Dudley L. Hascall, and others have attempted to modify or extend the theory.
Criticism The Halle–Keyser system has been criticized because it can identify passages of prose as iambic pentameter. Later generative metrists pointed out that poets have often treated non-compound words of more than one syllable differently from monosyllables and compounds of monosyllables. Any normally weak syllable may be stressed as a variation if it is a monosyllable, but not if it is part of a polysyllable except at the beginning of a line or a phrase. Thus Shakespeare wrote: × × / / × / × / × / For
the four winds blow in from every coast but wrote no lines of the form of: × × / / × / × / × / As
gazelles leap a never-resting brook The stress patterns are the same, and in particular, the normally weak third syllable is stressed in both lines; the difference is that in Shakespeare's line the stressed third syllable is a one-syllable word, "four", whereas in the un-Shakespearean line it is part of a two-syllable word, "gazelles". (The definitions and exceptions are more technical than stated here.) Pope followed such a rule strictly, Shakespeare fairly strictly, Milton much less, and Donne not at all—which may be why
Ben Jonson said Donne deserved hanging for "not keeping of accent". Derek Attridge has pointed out the limits of the generative approach; it has “not brought us any closer to understanding why particular metrical forms are common in English, why certain variations interrupt the metre and others do not, or why metre functions so powerfully as a literary device.” Generative metrists also fail to recognize that a normally weak syllable in a strong position will be pronounced differently, i.e. “promoted” and so no longer "weak." ==Magnuson–Ryder==