Can the ablative take a non-human agent or a human instrument?

Question

In the study notes for chapter 6 of Lingua Latina per se Illustrata, I read about the ablative of agent and the ablative of instrument or means:

In the passive, as we have seen, the personal agent is expressed by ab/ā and the ablative. When no person is involved, the ablative is used without ab/ā, e.g. Cornēlius equō vehitur; Lȳdia verbīs Mēdī dēlectātur

This seems to indicate:

• The act of a person (i.e., human) → ablative of agent → include preposition
• The act of a non-person (non-human) → ablative of instrument or means → no preposition

Are these firm rules? Or can a non-human be personified by including the preposition, or a human objectified by excluding it?

Answer 1

Yes, this is attested in Classical Latin, particularly in the case of the non-human serving as an agent (taking the preposition). Allen and Greenough, §405:

The ablative of the agent is commonest with nouns denoting persons, but it occurs also with names of things or qualities when these are conceived as performing an action and so are partly or wholly personified

As an example, they provide:

nē virtūs ab audāciā vincerētur (Sest. 92), that valor might not be overborne by audacity.

Similarly, Bennet (§216) offers:

hostēs ā fortūnā dēserēbantur, the enemy were deserted by Fortune
ā canibus laniātus est, he was torn to pieces by dogs.

Gildersleeve, §401, asserts that the substitution is permissible in both directions, that is, that a human can be objectified as well:

When the Instrument is personified and regarded as an Agent, or the Agent is regarded as an Instrument, the constructions are reversed. [...] So iacent suīs tēstibus, [Cicero, Pro Milone, 47] they are cast by their own witnesses; or, they are cast, their own men being witnesses.

Summary

These grammars provide numerous examples of the personification of a non-human as the agent in the ablative of agent, in which the preposition ab/ā is applied.

Examples for the objectification of a human person via the ablative of instrument, with no preposition, are apparently less frequent, but the construction is still permissible.

Answer 2

The following is my summary of Silvia Luraghi 2010 paper, in the tabular format (obviously, here I summarized those parts that are relevant to your question only). All the examples are hers, including the translation.

Luraghi 1986 writes that in Latin

“human agents are usually marked by a prepositional phrase introduced by the preposition ab, which takes the ablative case” whereas

“[n]on-human agents are marked by the simple ablative” (pp. 53-54).

Drawing on volume 2.1 of Leumann, Luraghi does mention that “in some cases, however, the preposition ab may be extended to non-human agents as well” but it happens in “[v]arious poetic occurrences, with verbs like mouere, agitare, uincere, e.g.

uinci a uoluptate

"to be overwhelmed by pleasure" (Cic.Off. 1.68).”

Leumann et al. argue it happens with verbs "die kraft ihrer Bedeutung den Agensbegriff suggerieren."

She concludes by saying that

“Non-human agents can receive the preposition ab in particular contexts, in which they are clearly connected to human activities,” e.g.

agros desertos a plebe et a cultura hominum liberorum

"fields abandoned by plebeians and by the care of free people" (Cic. Leg. Agr. 2.84).” (footnote 11)

Answer 3

Not only can animals and non-humans personified act as agent, but humans can act as instruments, as we see in Livy III.37:

Et decemvirí, quí prímó tribuniciós hominés, quia id populáre habebátur, circum sé ostentáverant plebí, patriciís iuvenibus sæpserant latera.