Existential theory was named by several philosophers and others who branched out in to another whole theory called "Absurdism". The question as to what the meaning of life is has been a very old thought process.Dictionary.com defines existentialism theory as “A philosophy that emphasizes the uniqueness and isolation of the individual experience in a hostile or indifferent universe, regards human existence as unexplainable, and stresses freedom of choice and responsibility for the consequences of one's acts." That being the case, it is not religion,but a philosophy of life.One of the most expressive definitions of this type of theory can be read in "Man's Search for Meaning" by Viktor Frankl Frankl was a concentration camp survivor who did believe that many people who survived did so because of their belief, or faith in something bigger.
Another type of belief is that life has no meaning, meaning IS life. There is nothing Biblical about this theory, it is more psychological or philosophical rather than a religious concept. Most people do not wish to have their beliefs tested by studying other systems of thought, because they hate to have them challenged. It is a truly liberating thing to take the time to study other systems, as it puts ones own life in perspective and also offers us understanding of why others belief systems are diametrically opposed to our own, or not.