In 1644 an order had been made that no book should be printed unless approved and licensed by the government. This is a part of Milton's great protest against trying to impose a censorship, instead of giving men freedom to choose.
Good and evil we know in the field of this world grow up together almost inseparably. He that can apprehend and consider vice with all her baits and seeming pleasures, and yet abstain, and yet distinguish and yet prefer that which is truly better, he is the true warfaring Christian. I cannot praise a fugitive and cloistered virtue, unexercised and unbreathed, that never sallies out and sees her adversary, but sings out of the race, where that immortal garland is to be run for not without dust and heat. Assuredly we bring not innocence into the world, we bring impurity much rather: that which purifies us is trial, and trial is by what is contrary.
If every action, which is good or evil in man at ripe years, were to be under pittance and prescription and compulsion, what were virtue but a name, what praise would then be due to well-being? Many there be that complain of Divine Providence for suffering Adam to transgress; foolish tongues! When God gave him reason, He gave him freedom to choose, for reason is but choosing. We ourselves esteem not of that obedience or love, or gift, which is of force: God therefore left him free, set before him a provoking object, ever almost in his eyes; herein consisted his merit, herein the right of his reward, the praise of his abstinence. Wherefore did He create passions within us, pleasures round about us, but that these rightly tempered are the very ingredients of virtue?
~ John Milton (1608-1674), Areopagitica