Despite his plan to give up sex and to enrich or feed his soul (as he declares in "Sonnet 146"), the speaker finds that giving up earthly desire is not so easy. Perhaps it is even impossible. In "Sonnet 147" the speaker admits that the lust within him is stronger than his soul.
In "Sonnet 146" the speaker describes his internal conflict and the anguish that he feels within himself in terms of body and soul.
In "Sonnet 147" the speaker once again suggests that the conflict within him is caused by the dual or two-part nature of man, but in this poem the two parts are referred to as Reason and Desire (or Emotion). Although the terms are different, they are related. According to Christianity at that time, the soul was the center or source of Reason, but desire is a condition of the body.
The reader may also find it helpful to view the structure of this poem in terms of the octet and sestet. In the octet the speaker explains how Desire is in not only in conflict with Reason but how Desire also appears to have defeated Reason. In the sestet the speaker then explains his state or condition now that his Reason is gone.
The sonnet begins with a simile. The speaker compares his love (that is, his earthly love or lust for the Dark Lady) to a fever (or to a disease that causes a fever) in the first quatrain. It is an appropriate simile. The heat of a fever is like the heat of passion,