If you claim that a life of physical suffering is worse than no life at all, then aren't you claiming that that highest of values, life, is in certain circumstances worth less than non-life?
The question of the moral permissibility of suicide for an egoistic philosophy is fascinating. It is challenging for Objectivism
, which defends man's life as its ethical standard; it seems that suicide must be ruled out as an option when life is the standard for ethics. Yet Ayn Rand
defended suicide as a viable option in her novels, such as when John Galt tells Dagny Taggart he will kill himself before allowing the government thugs to torture and kill her. I side with Galt, and my answer to your question is: Yes—there are situations in which suicide can be rationally defended within the Objectivist ethics of self-interest.
Let's start with Objectivism's standard for ethics. The Objectivist ethics rests on the standard of a meaningful life, or in Rand's terms, of "man's life qua man." The key to understanding how suicide can be logically defended depends on unpacking the pregnant second part of this phrase. There are various conditions that must be met for one to have a meaningful life. If those conditions are not being met, it is appropriate to end one's life. What are the requirements for a meaningful life?
I want to begin by acknowledging a perhaps obvious point. Being alive, in the sense of having continued physiological functioning of one's body, is the first necessary condition for having a meaningful life. However, I want to emphasize that while basic physiological functioning is a necessary condition for meaningful life, it is only one such condition, and it alone is insufficient for having such a life. There are other required conditions to be met that together are sufficient for having a meaningful life. If basic physiological functioning exists, but these other conditions do not, then life is not meaningfully human. If life is not meaningful, it is not therefore a human life, and it is permissible to end that life on the standard of "man's life qua man." Let me outline these other, less obvious, conditions.
The first condition is the possession of a conceptual consciousness. "Meaning" is a term which applies only to a conceptual consciousness. There are important features of such a consciousness that account for the unique character of human life compared with other kinds of life. It is only humans that organize experience into open-ended abstract categories, i.e., into concepts and propositions, and thereby experience life as "meaningful" in the relevant sense. Only a being that can create principles for use in guiding its actions can even contemplate the possibility of ending those experiences. Animals do not have this ability, and that's why they don't have a life of "meaning" in the way we do. If a person loses the ability to think conceptually, if a person's life will be reduced to the level of an animal, that person will no longer be capable of having a meaningful life, and he can rightfully end his life before it loses this essential human capacity.
The second condition is freedom. One must have the ability to act on one's conclusions to have a meaningfully human life. If one is physically prevented from carrying out one's plans, then one is enslaved. If one is enslaved to the point of being unable to act on his judgment at all, one has been reduced to a sub-human existence. This is clearly not a meaningful life. Once again, one would be utterly justified in ending such a life.
A third issue involves timing. For each condition described above, one would be permitted to end one's life when it becomes sub-human and therefore loses its meaningfulness. But this creates a paradox—if one is reduced to the state of being sub-human and one is thereby unable to act volitionally, how can one then end one's life? The answer is: one is permitted to end one's life while one still retains the ability to do so, but one should not do so unless this is an inevitability. The justification for ending one's life is appropriately separate from the timing of the action. Ideally, one should end one's life the moment prior to its becoming sub-human. Practically, if my experience as a physician is a good guide, one says good-bye to one's loved ones while still in reasonable possession of one's identity.
One additional issue is the question of determining "inevitability." It's notoriously difficult to know with certainty a future event. This uncertainty must be accounted for in the choice to end one's life. However, we must not fall into an intrinsic conception of certainty. We cannot demand omniscience. Further, the laws of causality hold. Sometimes, it can be known with certainty that one will soon be reduced to a sub-human existence, and when such a situation arises, it is perfectly appropriate to take action to prevent it.
Given the above, I know of two situations that can be defended as appropriate for suicide. The first is the loss of one's ability to experience life meaningfully due to the progression of an incurable, terminal illness such as cancer. The second involves the loss of one's freedom to such an extent that one can't act on one's judgment in any way. This would be the case of one imprisoned in a totalitarian prison or as a prisoner of a criminal. In both cases, one continues to possess physiological functioning, but one has lost another of the necessary conditions for meaningful life. The first involves the loss of a functioning conceptual consciousness as interminable pain becomes the entire focus of one's experience. The second is the loss of one's ability to act on one's own judgment. Either of these conditions would qualify as appropriate for suicide.
Now, you had asked about assisted suicide. In a libertarian governmental system, drugs of various kinds would be more widely available. So a physician's assistance to provide prescription drugs would not be necessary for assisted suicide. This is an issue on which Objectivism has no developed position, but it seems to me that in a free society it would be best for physicians to focus on healing and let the suicidal find other helpers. After all, one wants one's physician to have a focus on preserving life. But this, as you note, is a moral issue, and certainly in a free society assisted suicide would be within a person's legal rights.