In English poetry substitution, also known as inversion, is the use of an alien metric foot in a line of otherwise regular metrical pattern. [1] For instance in an iambic line of "da DUM", a trochaic substitution would introduce a foot of "DUM da".
In a line of verse that normally employs iambic meter, trochaic substitution describes the replacement of an iamb by a trochee.
The following line from John Keats's To Autumn is straightforward iambic pentameter: [2]
Using '°' for a weak syllable, '/' for a strong syllable, and '|' for divisions between feet it can be represented as:
° | / | ° | / | ° | / | ° | / | ° | / | |||||
To | swell | | | the | gourd, | | | and | plump | | | the | ha- | | | zel | shells |
The opening of a sonnet by John Donne demonstrates trochaic substitution of the first foot ("Batter"):
/ | ° | ° | / | ° | / | ° | / | ° | / | ||||||
Bat- | ter | | | my | heart | | | three- | per- | | | soned | God, | | | for | you | | |
Donne uses an inversion (DUM da instead of da DUM) in the first foot of the first line to stress the key verb, "batter", and then sets up a clear iambic pattern with the rest of the line
Shakespeare's Hamlet includes a well-known example:
In the first line the word that is stressed rather than is, which would be an unnatural accent. The first syllable of Whether is also stressed, making a trochaic beginning to the line.
John Milton used this technique extensively, prompting the critic F. R. Leavis to insultingly call this technique the Miltonic Thump. [3]
Sometimes the opposite substitution, of an iamb in place of a trochee, is found, as in the following lines from Shelley's Ode to the West Wind:
Here the words the leaves are an iamb (da DUM) in a place in the line where normally there would be a trochee (DUM da).
miltonic thump.