Thou blind fool, Love, what dost thou to mine eyes, (1)
The poem starts by addressing Love as a god. This tells us a few things right off the bat. First, we know that the speaker thinks of Love as something outside of himself, some force that swoops in and messes up his life. Also, because of what we know about gods, this reference shows us that Love is very powerful. From the first line, can we tell whether the god of Love is using his power for good or for evil? Not exactly—the speaker has just begun to ask the question, which won’t even be completed until the next line. But the abrupt, angry tone of the opening, "Thou blind fool, Love," suggests that it’s not going to be pretty.
That they behold and see not what they see? (2)
Now, the speaker finishes asking his question. The problem seems to be that Love has taken away the speaker’s ability to understand reality. What the speaker is saying is that his eyes look at something, and they don’t understand what they’re looking at. In a way, you could say that the somewhat confusing way the speaker has phrased this is a sign of the confusion that Love has brought to his life.
They know what beauty is, see where it lies,
Yet what the best is take the worst to be. (3-4)
Did you notice that the previous line of the poem still didn’t make it very clear what the speaker was talking about? Sure, he made it clear that he thinks Love has taken away his ability to understand reality, but did he bring in any evidence to back this up? Not so much. In these two lines, he makes things a little bit clearer: his eyes are experienced, they know what beauty is, but they can’t stop looking at the "worst" person in the universe and thinking that she (we're assuming it's a she) is the "best."
If eyes, corrupt by over-partial looks,
Be anchored in the bay where all men ride,
Why of eyes' falsehood hast thou forgèd hooks,
Whereto the judgment of my heart is tied? (5-8)
Ah, now we get it. The problem is that Love has made the speaker unable to take his eyes off a woman who cheats on him with "all men" in the world. Yikes. That doesn’t sound so good. But wait—it actually gets worse. It turns out that Love wasn’t satisfied just with making the speaker hooked on the appearance of this woman. Instead, he has used the speaker’s eyes as a way of getting at his heart. Now that his heart is attached, all bets are off.
Why should my heart think that a several plot,
Which my heart knows the wide world’s common place? (9-10)
Now we see the effects of that whole heart-being-attached problem. Even though the speaker knows, deep down in his heart, that his lady-friend is everybody else’s lady-friend too, it keeps telling him that she has reserved herself for him. Notice that, in these lines, the speaker has stopped explicitly blaming Love for his problems. In fact, from line 7 until the end of the poem, there will be no more mention of Love. Even in line 7, he is referred to only in a fairly indirect way, as "thou," which forces us to think all the way back to the beginning of the poem to remember who the speaker is talking to. Has the speaker changed his mind and decided that the god of Love isn’t really to blame, but rather his own heart and eyes? Who would you blame for this relationship hitting the rocks?
In things right true my heart and eyes have erred,
And to this false plague are they now transferred. (13-14)
Even though the poet has stopped speaking explicitly about Love, he seems to end the poem more in the grips of Love than ever. Even after everything he’s been through, he still feels that not only his "eyes," but also his "heart" have been "transferred" to his nasty lady. Yikes. Love is dangerous stuff. Like, they should put a warning label on it, or something.