The evil of marriage, as it is practiced in European countries, extends further than we have yet described. The method is, for a thoughtless and romantic youth of each sex, to come together, to see each other, for a few times, and under circumstances full of delusion, and then to vow to eternal attachment. What is the consequence of this? In almost every instance they find themselves deceived. They are reduced to make the best of an irretrievable mistake. They are led to conceive it is their wisest policy, to shut their eyes upon realities, happy, if, by any perversion of intellect, they can persuade themselves that they were right in their first crude opinion of each other. Thus the institution of marriage is made a system of fraud; and men who carefully mislead their judgments in the daily affair of their life, must be expected to have a crippled judgment in every other concern.You can read the book online here. The quote comes from this chapter.
Add to this, that marriage, as now understood, is a monopoly, and the worst of monopolies. So long as two human beings are forbidden, by positive institution, to follow the dictates of their own mind, prejudice will be alive and vigorous. So long as I seek, by despotic and artificial means, to maintain my possession of a woman, I am guilty of the most odious selfishness. Over this imaginary prize, men watch with perpetual jealousy; and one man finds his desire, and his capacity to circumvent, as much excited, as the other is excited, to traverse his projects, and frustrate his hopes. As long as this state of society continues, philanthropy will be crossed and checked in a thousand ways, and the still augmenting stream of abuse will continue to flow.
The abolition of the present system of marriage, appears to involve no evils.
William Godwin writes in Enquiry Concerning Political Justice: