Whatever reasoning for being we might “find within”, it is self-determined. Beyond surviving and propagating itself, life has, in particular our lives have, no other inherent purpose(s) beyond what we choose to apply to them.
The assignment of purpose to everything is called teleology, children are native teleologists and some never grow out of it. Such assignments have no bearing on the facts of the matter, and can lead to skewed understandings of reality.
Your question is an assumption followed by an incomplete analysis.
If life had no rational basis at all, there would be none. It might be said that life is guided by factors other than the rational, but upon inspection, rationality exists, even if we don’t understand it. Many fields of the natural sciences, particularly biology and cosmology have presented views and material facts on this.
As for ”no rational basis for some people”, are you not referring to the questionable/irrational ACTIONS of “some” people? People are often irrational, as are the views of other people about even nominally rational acts. As it is said that, ”one man’s garbage is another man’s treasure”, there is much to be said for which side you stand on.
This post was edited by Don Barzini at July 21, 2018 6:46 PM MDT
Who told you there is no rational basis to life? Why did you believe them? The bible says we were put on the planet to take care of it. Even people who don't like the bible agree with that.
If you don't have a belief in God or such, there is no rational basis to life since it's occurrence is based on chance. Also, if you do not believe in free will, which most metaphysical nihilist's do not since that would require a ghost within the machine, then again life is predictable.
If everything that we call heroism and glory, and all the significance of all great human achievements, can be reduced to some neurons firing in the human brain, then it’s all destined to be extinguished at death. And considering that the entire span of homo sapiens’ existence on earth wouldn’t even amount to a blip on the radar screen of a 5-billion-year-old universe, it seemed silly to pretend like the 60-odd-year life of some random organism on one of trillions of planets was something special.
As such you can act like life has meaning, but it doesn't in reality, they are just a mirage of chemicals firing in the brain. The part of the point of religion and philosophy is address questions that lurk beneath these natural rhythms, instead of just taking our feelings of meaningfulness as the alpha and omega of human existence.
In the context of the war, of course the battle feels meaningful. In the context of daily life as we experience it, of course our joys and sorrows feel intensely meaningful but just because we feel it does doesn't make it so.
There is no meaning to life, it doesn't matter if you are a murderer or a saint, you work in the soup kitchen, your children cure cancer, at the end of it all each person dies, years go by and then one day humanity will be wiped off the face of the earth, or the earth will come to an end and despite all those peoples feelings about the meaningfulness of life, it all ends in zero.
A materialist's view cannot have the best of both worlds many modern atheism deny that human consciousness is rooted in anything other than the chemicals in our brains, thus rejecting the idea that any of our experiences will last outside of time; yet it also tries to say that our consciousness and experiences are meaningful. I don’t see how both of those assertions can be true, maybe we have some gene that drives us to find meaning despite there being none.