Explanation: Just to elaborate a little on the answer, it can be added that the tone in this famous and beautiful sonnet (one of the more than a hundred that he wrote) is clearly romantic, since the speaker is praising the beloved one, establishing a comparison between him and the summer. The beloved one is, nevertheless, superior, "more lovely and temperate," and his beauty does not perish ("But thy eternal summer shall not fade / Nor lose possession of that fair thou ow’st [...]"), since it will always be preserved in this poem ("When in eternal lines to Time thou grow’st [...]").
Laertes' use of the word "subject" in two different meanings emphasizes his point about justifying Hamlet's indecision and melancholy. Hamlet may be a prince but his power is limited because he is "subject" or must submit to his fate or destiny. This strenghtens his argument.
