Porson's Law

Porson's Law, or Rule or Bridge, formulated by the British scholar Richard Porson (1759-1808), concerns the meter of Ancient Greek tragedy. It is very narrow in its scope: it applies only to tragic (not Comic) iambic trimeters (Porson's "senarii"), only to the third anceps of the line, and only when that anceps is followed by a word break; in these circumstances, Porson's Law states that the anceps, if long, must be a monosyllable.

In Greek prosody, shorter feet like the iambic (short-long) are counted in pairs, two feet constituting one "metron" or "measure" (short-long-short-long); so a line of six iambic feet is called an iambic trimeter, not, as it would be called in English prosody, an iambic hexameter. To relieve the monotony of endlessly alternating shorts and longs, certain variations are regularly permitted; notably, the first syllable of any "metron" may be long instead of short, and is accordingly called "anceps" (ambiguous, i.e. short or long); there are of course three "anceps" syllables in any iambic trimeter line.

Porson's Law can only apply to the third anceps, because a word-break after the first anceps would necessarily leave a monosyllable, and a word break after the second anceps would constitute a major caesura, for which different rules apply.

Goodwin's Greek Grammar (1895:358 §1660) helpfully summarises Porson's Law as "When the tragic trimeter ends in a word forming a cretic (¯ ˘ ¯), this is regularly preceded by a short syllable or by a monosyllable."

Porson's own, rather tortuous, formulation of his Law appeared in his edition of the Hecuba of Euripides (1802):

"Nempe hanc regulam plerumque in senariis observabant Tragici, ut, si voce, quae Creticum pedem efficeret, terminaretur versus, eamque vocem hypermonosyllabon praecederet, quintus pes iambus vel tribrachys esse deberet."

Translation: "That is to say, the tragic poets generally followed this rule in iambic trimeters: If a line ends with a word which produces a cretic foot (long-short-long), and if this word is preceded by a word of more than one syllable, then the fifth foot (i.e. the first foot of the third iambic metron) of this line must be either an iambic (short-long) or a tribrach (short-short-short)."

(If the last word of the line makes a pure cretic, the fifth foot must be an iambic; if an impure cretic, with the first long resolved into two shorts, the fifth foot must be a tribrach.)

"Non potuerunt igitur talem versum Tragici scribere, qualis est Κρύπτοντα χεῖρα καὶ πρόσωπον τοὔμπαλιν, aut Ἄτλας ὁ χαλκέοισιν νώτοις οὐρανὸν, aut Τὸ μὴ μάταιον δ᾽ ἐκ μετώπων σωφρόνων, certe noluere, si modo vel diversa orthographia vel alia verborum positura vitare possent 'In scenum missos cum magno pondere versus'." (Supplementum ad Praefationem ad Hecubam, p. XXX)

"Therefore, the tragic poets could not write lines such as [an adaptation of Hecuba 343, read ἔμπαλιν], or [compare Ion 1], or [Aeschylus, Supplices 198 (corrupt)]. Surely, they wouldn't, if, by a different spelling or another word order, they could avoid 'verses with heavy weight flung onto the stage' [Horace, Ars Poetica 260]."

Martin L. West (1987:25) has extended Porson's Law by stating it thus: "When the anceps of the third metron is occupied by a long syllable, this syllable and the one following belong to the same word, unless one of them is a monosyllable." This addresses also a (very rare) situation not addressed by Porson, where the word-break is followed rather than preceded by a monosyllable.

West observes that "there are very few exceptions in tragedy, most of them textually suspect."

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