Ways of Reading Third Edition - Martin Montgomery, Alan Durant, Nigel Fabb, Tom Furniss, Sara Mills 2007

17.4 Rhythm, metre and ‘foot substitution
Unit 17 Verse, metre and rhythm
Section 4 Poetic form

Much literary criticism that refers to the metrical form of a poem uses a notion of ’foot substitution’. We will explain shortly why we do not endorse this practice, but first we explain it.

This line is in iambic pentameter because it has five iambic feet (binary feet with the rightmost syllable the head). In explaining what a head of a metrical foot was, we earlier said that it ’tended’ to be a stressed syllable, but that it need not be. Our assumption was that a line is all in one kind of foot, and does not vary foot type within the line, and that any mismatches between the rhythm of the line and the metre of the line should be recognized as variations - as a gap opening up between the rigid metre and the more flexible rhythm. In this particular line, there are mismatches involving the first and fifth syllables (both of which carry stress but are not heads) and the eighth syllable (which does not carry stress but is a head).

The notion of ’foot substitution’ changes the metrical form to match the rhythm, by replacing feet with other types of foot:

The substitutions here include a spondee (a foot with two heads) and a pyrrhic (a foot with no heads) - two types of ’mutant’ foot that are found in English verse only as substitutions. This approach to feet implies that feet are a component of the rhythm of the line. We suggest that this is not the case: feet are a component of the metre of the line, but the rhythm - the actual performance of the line - is not composed from specific types of foot; instead the rhythm of the line can be thought of as approximating to the metre of the line. We think foot substitution is not a good idea, partly because it confuses rhythm and metre, and partly because it is terminologically over-complex (it requires more than the four basic feet) and describes details that do not clearly have any significance: what do we know when we know that the line begins with a ’spondee’? The only occasions when the notion of ’foot substitution’ is potentially useful are when it is used to describe very common rhythmic variations, of which the most common is for an iambic line to begin with a ’stressed- unstressed’ sequence:

I cannot rest from travel: I will drink

Life to the lees: at times I have enjoy’d

Greatly, have suffer’d greatly, both with those

      (Alfred Tennyson, ’Ulysses’, 1842)

All the feet in every line are iambic, but rhythmically the second and third of these lines begin with a stressed-unstressed sequence that is ’in counterpoint’

to the right-headed iambic foot. If this sequence was systematic across the line the line would be trochaic; as it is only in the first foot this is sometimes called ’trochaic substitution’ or ’trochaic inversion’. There is no actual substitution, but the term is a useful reminder of a common pattern.