The Transitivity Of Labile Verbs

the pot	broke
Actor/Medium	Process: material

I	broke	the pot
Initiator/Agent	Process: material	Actor/Medium

See Halliday & Matthiessen (2014: 339, 351-3).

Halliday & Matthiessen (2014: 340):

As we noted above, if we examine the lexis of modern English, and look up large samples of verbs in a good dictionary, we find that many of them, including the majority of those that are in common use, carry the label ‘both transitive and intransitive’. If we investigate these further, we find that where the same verb occurs with each of these two values the pairs of clauses that are formed in this way, with the given verb as Process, are not usually intransitive/transitive pairs but non-ergative/ergative ones. There are intransitive/transitive pairs, like the tourist hunted/the tourist hunted the lion, where the tourist is Actor in both. But the majority of verbs of high frequency in the language yield pairs of the other kind, like the tourist woke/the lion woke the tourist, where the relationship is an ergative one. If we express this structure in transitive terms, the tourist is Actor in the one and Goal in the other; yet it is the tourist that stopped sleeping, in both cases. Compare the boat sailed/Mary sailed the boat, the cloth tore/the nail tore the cloth, Tom’s eyes closed/Tom closed his eyes, the rice cooked/Pat cooked the rice, my resolve weakened/the news weakened my resolve.