meaning of the at once in the below sentence

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.