William Shakespeare's Sonnet 129 deals with the issue of lust and human promiscuity. Shakespeare explains his biting criticism of lust through fourteen lines of contemplation.
In the first eight lines, Shakespeare details just what lust is: "The expense of spirit in a waste of shame / Is lust in action: and till action, lust / Is perjured, murderous, bloody, full of blame, / Savage, extreme, rude, cruel, not to trust; / Enjoyed no sooner but despised straight; / Past reason hunted; and no sooner had, / Past reason hated, as a swallowed bait, / On purpose laid to make the taker made" (1-8). Shakespeare divides lust into two parts: lust in action and lust while it builds up.
Lust in action is referred to in terms of a sexual act: "the expense of spirit in a waste of shame" (1). The expense is release, while spirit refers to a person's inner life-force (or literal life-force for men). Thus for Shakespeare, sex for lustful purposes is completely pointless and will only bring shame. Moreover, Shakespeare hints that sex in lust is fruitless in terms of what it will bring sexually. In other words, sex for natural reproductive reasons has a purpose and thus is no waste. There is still an "expense of spirit" but it is for the betterment of man (reproduction).
Sex for lust on the other hand is just for personal gain and thus the "expense of spirit" is literally fruitless or a "waste" because it is not for reproduction. No good can from this lust because it is releasing evil into the world. After all, while lust releases the build-up of feelings and pent up energy in humans, these feelings are nothing short of a heinous.
According to Shakespeare, lust should never be trusted (4), and he goes so far to say that it: "Is perjured, murderous, bloody, full of blame" (3). Thus Shakespeare's feelings of lust at the ready, or building to the point of release are much like a murderer's thoughts. These feelings haunt and plague a human's mind, and they relentlessly toil away, bothering the human until the only option is release. Unfortunately, when humans act upon their lust, nothing is gained.
For one, the feeling of release is "Enjoyed no sooner but despised straight;" or hated as soon as the act is over. In addition, the release of lust has only allowed lust to spread and, worst of all, those that act upon lust don't even receive relief. Instead, the lust multiplies with each encounter, causing the unfortunate to go into a tormented madness (which is why they would be "Past reason") in which they can only focus on hunting for more (6).
Almost like a sickening infection, the lust spreads from person to person, and each one takes the "bait" (7). Shakespeare even states that those who are controlled by lust can only lure others into the illness, and thus lust is: "On purpose laid to make the taker mad" (8). Those who partake in lust are stricken themselves, doubling their feelings with a bitter hatred for those who corrupted them. In some senses, lust for Shakespeare can be seen as a threat and enemy to the common man. Moreover, it is very reminiscent of a venereal disease due to its associations with evil and almost like a trap for the non-infected.
In the last six lines, Shakespeare continues his description of lust: "Mad in pursuit and in possession so; / Had, having, and in quest to have extreme; / A bliss in proof, and proved, a very woe; / Before, a joy proposed; behind a dream. / All this the world well knows; yet none knows well / To shun the heaven that leads men to this hell" (9-14). Those infected by lust almost literally become insane, or "Mad in pursuit and in possession so" (9). Striving to capture and control the lust, humans who are plagued are obsessed with "had, having" or seeking sex in "extreme" ways.
While Shakespeare admits that acting upon lust is "A bliss in proof" or pleasure in experience, it is still a "very woe" (11). Moreover, those who have not yet taken this pleasure, but plan to, are "behind a dream" (12) for they do not see what could go wrong in their "proposal" to act upon lust. Yet, as Shakespeare states, even when the world is wary of the evils of lust, it still continues to act upon it and, thus, while they know, they still don't "know well" (13) enough "To shun the heaven that leads men to this hell" (14). Lust is referred to as heaven because of its pleasure upon release as well as supposed joys, but its true form is in the form of hell.
Overall, this is a fascinating and excellent piece written in iambic pentameter that attempts to explain not only how evil lust is, but how humans can still partake in it after finding out (they go mad).