value of life? Well, this is theoretical, very general question may actually depends on whose life it is that you are talking about and how you define 'value'. Then again, it may be a meaningless question that may be rhetorical and a red herring since life may have no 'value' or no 'purpose' and may simply be that which the person makes it.
Let's examine these questions from four different perspectives: the question itself (What is the value of life); whose life; religious perspective on the matter; sociological perspective on the matter. We will then proceed to examine the question from the perspective of diverse thinkers.
What is the value of life
We can talk about something having value when we touch it, feel it, examine it under the microscope, assess it in various ways and can physically measure it against something else. In other words, we can far more objectively and assuredly tag value onto something that is physical rather than something that is not. Compare for instance, to the metaphysical factor of 'love'. Now, artists, poets and so forth may describe this as a valuable sentiments but since it is an emotion that exists in the abstract and since we can neither measure nor evaluate it, we cannot touch it, place it under the microscope, come to any unequivocal agreement about it and, therefore, we cannot accordingly measure it nor tag on it a certain percentage of value. The same exists with any metaphysical factor, and 'life' is no exception.
The question of 'value' or purpose of life is -- as positivists would argue -- a meaningless one, particularly since life may have no purpose.
What is the 'value' of life also turns around on the definition of 'value'. Should this consist of happiness or morality, or substance and, if so, in terms of which substance? One answer is that value is defined as the circumstance where the individual has chosen worthy choices (Nielsen 1964) or achieves satisfaction in his life's choices (Wohlgennant 1981). However, these answers too are subjective and broad; whilst one may concur that the individual's life may be valuable, another may disagree. Others say that the choices are those that render a life coherent and transcend human nature as well as make it intelligible (Levy 2005). Philosophers are still conflicted about what it is that makes a 'meaningful' life; after all we each have different perspectives.
2. Whose life?
The question (of a meaningful life) too is rather unclear and vague. Life is a possession not only of humans but also of animate things all along the spectrum suchs of plants, animals, and so forth. We gather that life here refers to anything that is breathing; but wouldn't life be more valuable for humans than for plants? It certainly seems to be so since humans make no fuss of eating plants. Moreover, even as regards animals, humans make less of a fuss of consuming animals than they do of consuming one another. During, at least, the current period of our history human life seems to be more expensive than that of animal life. Therefore we may conclude that human life has more value.
Then again, isn't that a social-constructionist phenomena since in some countries during some historical eras, human life was cheaper than that of animals. And certain human life, still today, is in certain countries, still cheap. So, perhaps, therefore, the answer too varies according to geography and history as well as to political circumstances.
What about economic circumstances? Aren't successful people, wealthy people, celebrities, more important than other individuals. For instance, wouldn't; the life of Obama be considered be valuable than that of a tramp (at least to some)? And may others not consider scientists more worthy and valuable than let's say the hooligan of the street? During World War II, only a certain amount of tickets were given to people who tried to flee Nazi-dominated countries. America carefully selected its immigrants choosing only those whose lives they considered it most valuable to save. In this way, therefore -- depending on whom you ask -- the life of certain people and animate things may have more value than that of others. A woman for instance may consider the life of her beloved dog to be more valuable than the life of a prominent stranger. The value of life is therefore subjective. We may posit that it is more valuable to the owner than it is to an outsider; but then again some owners wish to dispossess of their lives as fast as they can. To them their lives have no value.
3. Religion and the value of life
Theology and belief systems have their own ideas regarding value of life. Judeo-based religions, for instance, affirm that man is created in the image of his or her creator and therefore possesses intrinsic value. The more he or she become Divine and uses her potential in as valuable way, the more valuable her life becomes.
Buddhism, however, may have a different idea of life. To them, life is suffering. Death which symbolizes release of suffering and more substantial eternity and existence may be more valuable than life. Certain belief system has a similar position today.
Other perspectives, however, such as atheism may place far less value (to none at all -- for instance certain strands of existentialism) on life. After all, existentialists, for instance, see life as a meaningless bauble that goes on and one in a tiring nonsensical senseless motion. Life is stupid; it has no value. This would have been Schopenhauer's pessimistic stance. It may have been Kierkegaard's too for all his religious postulating. It is debatable whether or not this was Nietzsche's. Although Nietzsche may have said that the life of the Superman has value; the life of the herd less and this consists largely of assisting the Superman.
Other existentialists, however, may attribute a greater substance to the value of life possibly taking the Socratic approach that life's value depends on what you make of it. Compare it to the germ of life in an oak tree. The oak tree has potential to become something magnificent and to give shade to so many people. Or it can refuse to grow and stunt. If you think that the quality of providing shade is important as well as that the idea of beauty and growth has merit, well then you may consider the life of the oak tree to be worth something, since its life has value. The same applies to the life of any animate being: to the extent that it uses its potential, thus the extent of the value of its life. Religion, therefore, gives its own answer to the value of life.
4. Sociology and the value of life
The value of life too differs according to cultures with some cultures respecting and valuing life more than others. Western cultures, for instance, may value life more than that of struggling individuals in certain other cultures. We know, for instance, that certain people in some Islamic cultures are all too keen that they and their children become shahid i.e. martyrs since they see life as possessing value in killing others. This gives their life meaning. Religious fundamentalists of many other groups have had similar ideologies, and so to such people, life may only have value when it is sacrificed for a cause.
In such a manner, we may divide the perspective of religions and societies on the value of life into two categories: God-centered views and soul-centered views. The former bases value of life on connection with a God; the latter bases it on connection with a soul (and may not necessarily believe in a God).
The God-centered view is not only that God created person in His image but that he also gave man to purpose with which to conduct his life and that each and every person is important even in a miniscule way.
The soul-centered view echoes that of Tolstoy who argued that creating an act of purpose gives life meaning and that to make this difference to the world requires having a soul (Morris 1992, 26).
Other approaches on the value of life
Other perspectives that do not believe in God or soul assume a subjectivist stance and argue that it is love that provides the greatest value for our existence (e.g. Frankfurt 2002, 250). Meaningfulness, they argue too, should be approached from the stance of what the individual person finds valuable form life and meaningful for her. In this way, the view is a subjective one. Frankfurt (1982) further argues that meaning can be gained from losing oneself in work that is meaningful and absorbing to one. However, what if one is using this absorption to harm others: is one's life valuable then? Hitler, for instance, was totally absorbed in his work and found meaning in it: can we say his life was valuable?