Milton's "Truth comes into the world like a bastard" means???

More precisely Truth never comes into the world but like a bastard, to the ignominy of him that brought her birth

So. . . how is “truth” like a bastard?

Saint Louis University knows more about it:

My first thought would have been that what Milton wanted to say was that truth was brought to thee world by people who did not really want to do so, but apparently he’s alluding to the legal principle (back then) that an illegitimate child was not to be considered a relative to his or her father and was therefore the child of only one person.

Edit: Coding

He’s simply saying that pointing something out for the first time never made anyone popular. He is contrasting this with ‘Custom’, received ideas that get accepted by everyone uncritically.

Whether this claim is actually true is another matter. But this comes from the preface of his revised edition of his Doctrine and Discipline of Divorce. He knew that its support for divorce had already encountered widespread ridicule. So he wasn’t exactly being unbiased in suggesting that those who identify ‘Truth’ are too easily dismissed.