It is clear to me that it is necessary to make a disclaimer before this writeup. I do not condone suicide. This is not in any way meant to convince others that suicide is a good idea. What it is intended to do is to make the argument that the act of taking ones own life in and of itself is not morally wrong. That is not to say that the consequences of such an act are not reprehensible and worthy of avoiding nor that my arguments are in any way solid or sound.
In general, there are a few arguments against suicide as a right. I will deal with the arguments one by one. For the purposes of expediency, I will ignore all the theological arguments for or against suicide because, being a nontheist, I know very little about religion and feel that arguing the theological aspects of suicide is a pointless waste of time seeing as the existence (or non-existence) of God itself is unprovable.
As a side note, when I refer to something as right, I mean to say this: an attribute or ability which others cannot violate morally and which does not violate the rights of others. I would also like to welcome any well thought out counter-writeups or writeups which concern the theological aspects of suicide which I have skipped over here.
The Right to Life Argument.
1) You have no right to violate your own rights.
2) The right to life is a right.
3) Suicide violates your right to life.
4) Suicide violates one of your own rights.
5) Suicide is not a right.
This first argument comes from one of the natural rights we all accept; the Right to Life. A person making this argument would claim that no one has the right to violate rights, even their own. While this is true, suicide does not necessarily entail violating one's right to life; instead it is the relinquishing of that same right. We, as a society, give up our rights all the time and few argue that we don't have a right to give up our rights. In fact, the ability to give up our natural rights is central to the concept of the social contract, one of the ideas upon which modern government is based.
Assuming there is not a draft, people who choose to go into the armed forces willfully renounce many of their rights upon enlisting. It is assumed that everyone has the right to enlist (whether or not the military will accept them) and thus, by parity of reason, everyone has the right to give up their own rights. Citizens have the right to vote in elections for their leader but every year in the US at least 40% of people choose not to exercise that right. Likewise, a person can choose not to exercise their right to life as it applies to themselves.
The Suffering Argument.
1) You do not have a right to intentionally inflict unhappiness on others as a result of your actions.
2) Death inflicts unhappiness on others.
3) Suicide is the intentional death of oneself.
4) Suicide is an intentional action that inflicts unhappiness on others.
5) Suicide is not a right.
Again, I disagree, most especially with the first premise. Inflicting unhappiness on others as a result of our actions happens all the time and is an unavoidable consequence of living in a social society. Mill realized this implicitly, as he repeatedly defined a moral action as something that produces the greatest amount of happiness or reduces the greatest amount of unhappiness.
Were the first premise a universal right, it would be constantly violated. That is not to say that the violation of a right is an indication that it is not a right. Wars go on and (mostly) men are killed daily, even though it is widely accepted that there is a right to life. However, the greater the amount of violation of a right during normal and moral circumstances, the more likely that it is, indeed, not a right in actuality. Imagine that it's not working out between you and the person you're dating so you end it. Though not the goal, you have created unhappiness but none would say that you had no right to end the relationship because of the unhappiness it causes. A different situation—a child in a store demands that his mother buy him a toy. The mother says no, which makes the child unhappy and he begins to cry. No one would argue that the mother was immoral by not buying the toy for her son.
Simply put, premise one implies that one has a right to not have unhappiness inflicted upon them by the intentional choices of others. In this sense, the first premise severely restricts another right which we hold as paramount: the right to choose one's own destiny--the right to free will. Because of this, we can't hold the implication of the first premise as a true right. With the first premise disproved, the argument is invalidated as it stands.
A person making this argument may then change their argument to sidestep the arguments against. They might alter their statement to say you do not have a right to intentionally inflict that magnitude of unhappiness on others as a result of your actions. This, however, is a non-argument because it leads us immediately to the question: how much unhappiness and from what cause is permissible? If the answer is that the amount of unhappiness caused by death is too much, then we're lead to the conclusion that death of any kind, whether suicide or not, is not a right, something which is manifestly untrue. If the answer is that the amount of unhappiness caused by suicide is too much, then it simply begs the question. So the only recourse for the individual making this argument is to come up with a quantitative measure of happiness and then decide on a permissible level, all the while avoiding arbitrary judgements.
Because of the flaws inherent in the first premise, we can't accept the conclusion as coming from a sound argument.
The Property Argument.
1) You have a right to treat your property however you wish.
2) Your body is not your property.
3) You do not have a right to treat your body however you wish.
4) Suicide is treating the body by destroying it.
5) Suicide is not a right.
From this argument follows the question, if you do not own your body, who does? Many philosophers in the past have argued that God owns your body. However, as stated above, I will not get into that claim. Others (especially after the rise of the state) have claimed that the body belongs to the state. If the body does indeed belong to the state, then it is given as a part of the social contract, otherwise it would be implied that none own the body in the state of nature.
Indeed, it may be argued that none own the body, just as none own the stars or the moon or the universe. This Romantic argument is true because of a lack of capability, not because of a metaphysical block--the conclusion is true but the premises are false. Ownership derives from the power to achieve dominion over an object. As a race, we are by and large unable to impose our will upon extraplanetary things. World domination is arguably still beyond the grasp of any modern organization. Thus it is true that none own the moon or the Earth.
However, from this definition of property and ownership, we can determine that we (our consciousness) have ownership over our bodies. Our minds inherently have dominion over the body--we can control our physical actions and physically alter or maintain our bodies. Nothing can end this dominion, it only ends with death which destroys both the mind and the body. Thus, if we have control over our own bodies and this control cannot be removed, we own our bodies as property and can do with them as we will.