Can you explain this quote from "Hamlet?" "
The virtue of his will: but you must fear,
His greatness weigh'd, his will is not his own;
For he himself is subject to his birth:
He may not, as unvalued persons do,
Carve for himself; for on his choice depends
The safety and health of this whole state;
And therefore must his choice be circumscribed
Unto the voice and yielding of that body
Whereof he is the head.
Laertes is here revealing several motifs of the play, including that of Denmark as a prison, appearances as opposed to reality, & Hamlet's approach/ideas about love. We also see Ophelia for the first time, in the context of her relationship with her brother.
It is clear that Laertes cares for Ophelia, in that he is warning her against putting too much stock in Hamlet's vows of love. He repeats the word "fear" later in this speech as well, perhaps attempting to solidify that idea in her mind, & emphasize the consequences of failing to heed his advice. Hamlet's mind & desires are not his own, as "subject to his birth", he must consider the state of Denmark before he makes any choices. Thus, Denmark is a prison for Hamlet, where he does not have the freedom that "unvalued persons do". All decisions must be weighed for the best interests of the nation, not just himself.
Also, this idea of Hamlet is different than we've seen previously. Laertes talks of Hamlet as a leader, tied to his political duties. But he is not king, nor does it seem like he'll become king any time soon. In fact, he seems utterly uninterested in the political aspect of ruling; his only interest is the usurper of the throne, Claudius.
Finally, this quote reveals one aspect of Hamlet's love. It is obvious that Laertes holds no stake in Hamlet's claims of affection, & his warnings to Ophelia may represent an attempt to control her. Or, it could just be a concerned brother warning his sister. There are many interpretations of Hamlet's actions, & the responses of other characters to them.
The lines you quote are from Act I, Scene 3. In this scene, Laertes, who is going to France, is saying good-bye to Opehlia.
As he says his farewells, he is also cautioning her about getting involved with Hamlet.
In the lines you mention, he is telling her that Hamlet is too important for her. He may love her, says Laertes, but he is not completely independent. Because he is such an important person, he may have to marry for political reasons. Because of this, he wants her to be careful about falling in love with Hamlet.