Gower's previous works had been written in Anglo-Norman French and Latin. It is not certain why he chose to write his third long poem in English; the only reason Gower himself gives is that "fewe men endite In oure englyssh" (prol.22–23). It has been suggested that it was the influence of Chaucer, who had in part dedicated his Troilus and Criseyde to Gower, that persuaded him that the vernacular was a suitable language for poetry, and the influence of Chaucer's Legend of Good Women has been detected in the Confessio (Macaulay 1908:166).
With the exception of a 74 line letter "unto cupid and to venus" in Book VIII, Gower did not adopt the new pentameter with which Chaucer had recently been experimenting, and which was in the 15th century to become the standard metre for English rhyme. He retained instead the octosyllabic line that had previously been the standard form for English poetry, and wrote it in couplets, rather than in the stanzas he had employed in his previous works. Gower characterised his verse in the Confessio as the plain style.
This decision has not always met with appreciation, the shorter lines being sometimes viewed as lending themselves to monotonous regularity, but Gower's handling of the metre has usually been praised. Macaulay (1901) finds his style technically superior to Chaucer's, admiring "the metrical smoothness of his lines, attained without unnatural accent or forced order of words". The work's most enthusiastic advocate was C.S. Lewis, who, though admitting that the work can be "prosaic" and "dull" in places, identifies a "sweetness and freshness" in the verse and praises its "memorable precision and weight" (Lewis 1936:201). Not all assessments have been so positive: Burrow (1971:31) describes it as "not so much plain as threadbare", and notes that the selective quotations of previous critics have served to draw attention to sections that are better poetry, but unrepresentative of the work as a whole.
The language is the same standard London dialect in which Chaucer also wrote. Gower's vocabulary is educated, with extensive use of French and Latin loans, some of them apparently original; for example, the Confessio is the earliest work in which the word "history" is attested in English (OED). That the work was aimed at a similarly educated audience is clear from the inclusion of Latin epigraphs at the start of each major section.