The problem of being is the central and fundamental problem of philosophy.
This problem may be simply stated as follows: What is being?
Or more precisely, which has primacy in the concept of being:
essence or existence?
Essence is what a thing is and
Existence is that a thing is.
The branch of philosophy that deals with this problem is called
ontology.
In the attempt to answer this problem, philosophy has developed various
solutions. The history of philosophy is the history of these solutions
and attempt to develop the philosophy of being or an ontology.