Linguists Morris Halle and Samuel Jay Keyser developed the earliest theory of generative metrics — a set of rules that define those variations that are permissible (in their view) in English iambic pentameter. Essentially, the Halle–Keyser rules state that only "stress maximum" syllables are important in determining the meter. A stress maximum syllable is a stressed syllable surrounded on both sides by weak syllables in the same syntactic phrase and in the same verse line. In order to be a permissible line of iambic pentameter, no stress maxima can fall on a syllable that is designated as a weak syllable in the standard, unvaried iambic pentameter pattern. In the Donne line, the word "God" is not a maximum. That is because it is followed by a pause. Similarly the words "you, mend," and "bend" are not maxima since they are each at the end of a line (as required for the rhyming of "mend/bend" and "you/new.") Rewriting the Donne quatrain showing the stress maxima (denoted with an "M") results in the following: