Which preposition to use with illiterate

in Occurrences 3%

I was never so illiterate in man.

to Occurrences 2%

They were illiterate to the last degree, so there is but one theory, they were inspired.

as Occurrences 1%

For the rest, it was perfectly clear that the monarchy had done nothing for the material or spiritual advancement of the country, which remained as poverty-stricken and as illiterate as it well could be.

of Occurrences 1%

He wished, I imagine, to give some idea to the young illiterates of the simple laws of motion and force.

under Occurrences 1%

No child under 14 and no illiterate under 16 and over 14 may be employed in any factory or mercantile establishment.

Which preposition to use with  illiterate