I don't really understand what John Milton means by "shutting his Parkgate" in his speech Areopagitica.
What is the meaning of this sentence: "And he who [...] by shutting his Parkgate" found on page 10 of Areopagitica by John Milton?
A SPEECH OF Mr. JOHN MILTON
For the Liberty of UNLICENC'D PRINTING,
To the PARLAMENT of ENGLAND.
Seeing therefore that those books, & those in great abundance which are likeliest to taint both life and doctrine, cannot be suppresst without the fall of learning, and of all ability in disputation, and that these books of either sort are most and soonest catching to the learned, from whom to the common people whatever is hereticall or dissolute may quickly be convey'd, and that evill manners are as perfectly learnt without books a thousand other ways which cannot be stopt, and evill doctrine not with books can propagate, except a teacher guide, which he might also doe without writing, and so beyond prohibiting, I am not able to unfold, how this cautelous enterprise of licencing can be exempted from the number of vain and impossible attempts. And he who were pleasantly dispos'd could not well avoid to lik'n it to the exploit of that gallant man who thought to pound up the crows by shutting his Parkgate. [John Milton]
In this passage, Milton is discussing the possibility, wisdom and practicability of censuring unsavory books in reference to "Spanish licensing." The books under question are what Milton classifies as books that "taint both life and doctrine." His argument is that common people without higher learning can acquire learning that is "hereticall or dissolute" quite easily in many other ways, particularly from the learned who are drawn to disputatious (questionable) books. He further declares that "evil manners" are "perfectly learnt a thousand other ways" without the help of questionable books.
Milton's conclusion therefore is that though there are some who might be disposed (inclined) to attempt to suppressed the books in question as they relate to Spanish licensing issue, all efforts at suppression of said books would be like someone trying to keep crows imprisoned by shutting the gates to his/er estate park grounds. This would be a foolish and futile effort to imprison crows (which destroy agricultural fields) because crows would simply fly right up and over the gates and away--to the grain fields. In other words, it is impossible to imprison crows by putting them behind a gate, and it is equally impossible, in Milton's opinion, to protect minds against the books in question by suppressing them.