His choice of language is used to appeal to the women's tendency (especially in the renaissance) to feel as if they are not worthy or pretty enough if they don't marry early in life. The speaker is appealing to the mistress's desire of marriage to convince her that if they had sex, it would bring them closer to marriage. The speaker uses his language not only to feed the mistress's desires, but to feed on her fears of being an old maid because she is cold and prudish. The speaker implies that every time he mentions sex, it "make(s) you apt to kill me" (16), meaning that she turns him down every time he mentions sex to her. The speakers choice of wording makes the mistress seem as if she is a tease and cruel, which usually are not attributes that women like to hear pertaining to them. The speaker believes that by making her feel like she is being cruel, she will try to make it up to him by doing what he wishes, which is have sex.
Symbols are another device that the character uses throughout the poem to represent desire, and to appeal to the desire of his mistress. The use of the flea is an obvious symbol of sex, and of the speakers" desire for the union of their two bodies. The man believes that the "flea is you and I" (12) and that it represents the coming together or mixing of the two bodies. The character also talks about their love as if it were a living thing which is as much as a real, breathing presence as either him or her. The speaker tells the mistress that within the flea is "three lives" (10), the blood of him, the blood of her, and the "blood of innocence" (20), which represents the product of their love. The speaker tries to convince his mistress that if the flea is killed, the love, as innocent and defenseless as a baby, will perish along with it, which appeals to the maternal instinct of women. The speaker, once again, focuses on what he believes to be the mistresses" fears, and tries to allay them.