Seneca contrasts faculties of humans and the other animals.
Nulli nisi homini concessa prudentia est, providentia, diligentia, cogitatio, nec tantum virtutibus humanis animalia sed etiam vitiis prohibita sunt. Tota illorum ut extra ita intra forma humanae dissimilis est ; regium est illud et principale aliter ductum.
I was doing fine until I ran into
regium est illud et principale aliter ductum.
illud: antecedent?
regium, principale, illud, and ductum may agree: neuter, singular
The passage seems to offer many variants in the manuscripts, which may be an indication that it is/was difficult to understand or corrupted.
regium illud et principale is apparently Stoic lingo for Greek to hegemonikon, the soul’s leading faculty, i. e. the closest equivalent to what we would call “the mind” (cf. Kaster & Nussbaum, Anger, Mercy, Revenge, 2010, p. 103, n. 59).
Est > "there is (to animals) > “Animals have the-soul’s-leading-faculty organized(?) in a different way”.
The following sentence makes thing clearer: Vt uox est quidem, sed non explanabilis et perturbata et uerborum inefficax, (…) ita ipsum principale parum subtile, parum exactum.
“In the same way as they have a voice, but not intelligible, (…) similarly their leading-faculty itself [is] insufficiently fine, insufficiently precise”.
OLD references rēgium and prīncipāle of this particular locus (sub uocibus), translating them ‘governing principle’ and ‘the ruling or authoritative part (of the mind)’, respectively. You could almost take them as hendiadyoin, I think. Kaster translates (in the book Shenoute mentioned): »Their entire constitution, inside and out, is unlike the human: their ruling principle is differently fashioned.» So he takes dūcere in its meaning ‘to fashion, shape, mould’, the 23rd subsection in OLD.
Shenoute’s and Timothée’s interpretation seems right to me. I have to confess I was stumped here, and didn’t have the time yesterday to dig into it further.
Just as an explanation: I thought I caught the meaning of the sentence. My difficulty was that I didn’t understand how the words produced the meaning. The meaning seemed clear from the context, I thought.
“Do we take illud as a demonstrative adjective?” Yes, modifying regium, which is a neuter adjective used as a noun, as Timothée points out. And principale is also a neuter adjective used as a noun, and is coordinate with regium, i.e. regium et principale, which together function as a sort of hendiadys.
