John 9:19

And they asked them, saying, is this your son
The first question they put was, whether the man that stood before them, pointing to him, was their son or not; whether they knew him by any marks to be their son, and would own him as such: had they answered to this in the negative, they would have got an advantage against him, and would have convicted him of a lie, since he had given out that he was the son of such parents; and proving such a lie upon him, would at once have brought the whole affair into suspicion at least: they add,

who ye say was born blind;
this contains a second question, whether, if this was their son, he was born blind or not; and if he was not born blind, though he had been blind, it would have greatly lessened the miracle: and besides, they would have put other questions upon this, whether his blindness was real, and by what means it came. Next follows a third question,

how then doth he now see?
By what means has he received his sight? They might hope, that if he was their son, and was really born blind, that he had his sight some other way than by Jesus; or they might object this to his being born, blind, as being a thing impossible, or at least not credible that he should ever see, was that the case.