meaning of the at once in a sentence

Question

I am translating the book Missing Out: In Praise of the Unlived Life by Adam Phillips. It has this passage:

There is, in other words, a difference between somebody saying something that makes one feel understood and somebody saying something striking. There is, or there can be, a difference between reading something intelligible and reading something that has a powerful effect; between words as procurers of experiences and words as consolidators of knowledge. There is a difference between the wish to comfort and assuage and the wish to provoke and unsettle. And we speak to each other and read for both these opportunities, and for other experiences as well. But it is the linguistic arts that seem at once hospitable to the notion of intelligibility, and in which intelligibility can be put into more or less intelligible question.

my problem is in this sentence:

But it is the linguistic arts that seem at once hospitable to the notion of intelligibility, and in which intelligibility can be put into more or less intelligible question.

please confirm if this is the correct understanding of the sentence:

1- the linguistic arts are at the same time are hospitable to the notion of the intelligibility and in them the intelligibility can be put into question

please note that the text is difficult and needs reflection to understand. It is not a novel or a news in which you get the meaning by just looking at the text. This book is written in philosophy/psychoanalysis field.

Answer 1

My judgement is that the sentence is ungrammatical.

• ' ... seem at once X and Y' is short for ' ... seem at the same time to be X and Y' or more commonly ' ... seem to be both X and Y'.

For example

• 'The foxes seem at once curious and wary'

is a (very formal, perhaps literary) shorter paraphrase of

• 'The foxes seem curious and/but at the same time they seem wary'.

Note that this is a metaphorical usage of 'at once' / 'at the same time', unlike the literal ('at the same instant') usage in 'computers can perform many tasks at once'. These phrases may be substituted by 'both' (or 'not only ... but also'):

• 'The foxes seem both curious and wary'

But 'seem in which intelligibility can be put into more or less intelligible question' is unacceptable.

I'd amend to

But it is the linguistic arts that seem hospitable to the notion of intelligibility; further, it would seem / it is a fact that this intelligibility can be put into more or less intelligible question.

'To put N into question' for 'to investigate' (perhaps?) is highfalutin' too.