I want to know if philosophers have attributed intrinsic value to being alive.
What I mean by this is, does being alive, whether a bug or a human, or a plant itself have meaning just simply by "existing" or must people and living things apply meaning?
1) Your question concerning the value of life has been answered differently. The answer depends on the worldview of the person who gives the answer.
E.g., according to the Jewish and the Christian religion life and human life in particular has a high value in itself (intrinsic value).
On the other end of the spectrum we have people who emphasize just the opposite assessment: Life has no value in itself. As a consequence it is up to each person to determine the length of his life and in particular to end his own life by suicide.
2) You also ask about the meaning of life. Also this question has been answered differently.
In most cases an atheist will deny that life has a meaning by itself. Instead it is the task of each individual to give an individual meaning to his own life.
While based on a religious worldview the meaning of human life could be worshipping a deity or qualifying for a pleasant afterlife.
Note. The two concepts meaning of life and value of life are related but not identical.
Certainly. This can be expressed in many ways. Kant, for example, develops both reason and moral freedom around the idea that all human beings or rational beings must be treated as "ends in themselves" never as means only. Most theologies or philosophies with a moral dimension have something akin to this assumed "intrinsic value" of human life.
Your question then becomes, does this also extend to all life? Buddhism, for example expressly extends this value to "all sentient beings," which probably does not include plants or bacteria. The Pythagoreans extended such value to some plants, beans for example.
And here we simply run into the ecological interdependency of life and even the definition of "life." We cannot live without consuming other forms of life. Does that mean we "value" them or that they have "intrinsic value"? I think it must almost be an a priori assumption that life "values" life, since it depends on it, and that only living things can "value" things, both living and nonliving things. So anything we might call a value system does assume an "intrinsic value" of life, if only to avoid internal contradiction.
But such a general, universal "value" is nearly empty of content. It would not tell you whether or not to kill eat beans or kill Persians. Perhaps a better way to approach the question is in reverse. What sort of value system might value something more highly than "life itself"? Can we imagine anything of such value that we would consider eliminating all life to preserve or advance it?
The idea comes very close to absurdity. Nonetheless, it has been a source of some compelling thinking, as in Nihil Unbound by Ray Brassier. We might imagine some sort of God or otherworld or afterlife or even AI singularity that is of higher value than "this life." ISIL, for one, appears to doctrinally destroy "this life" in favor of another. Marxists might argue that Capitalism, if it can be said to have a philosophy, progressively transforms life itself or "species being" into nonliving goods, machinery, and waste. Thus self-accumulating Capital enmeshes us in a higher value than "life itself."
But even these examples are not so much negating life itself, as imagining life in a more "valuable" form.The nihilist or even the Schopenhauerian pessimist may see no intrinsic value in this life or that life or even human life per se. But in my view to say "life itself has no intrinsic value" is simply nonsensical. So we might say that all philosophies, all forms of communication, presuppose an "intrinsic value of life" as the basis of any sort of evaluation or judgment whatsoever, philosophical or otherwise.
