Do you ever feel like nothing matters? Don't. There is one perennial existentialist question that philosophers all hinge modus operandi upon; In the absurdity of existence, does what I do matter? In order to answer that, you must have an understanding for what is and what isn't, and why it matters.
This leads to the most basic axiom that a human being who is aware of his subjective experience is confronted with - "The axiom of empty set" which poses, "There is a set such that no set is a member of it" or in other words, there is nothing and there is something - and the human experience can only come to know something objective through his subjective experience. To know your mother exists is the experience of knowing your mother - the biological implication of knowing relies on the objective causal circumstance of your mother being knowable. It is only that you come to know objective reality as the experience of you that the axiom of empty set can mean anything at all, because the dichotomy of empty and non-empty objectivity is subjectively experienced.
This is why the axiom of extensionality, which tells us that two sets are equal if and only if they have precisely the same members. Given any set A and any set B, if for every set X, X is a member of A if and only if X is a member of B, then A is equal to B. This shows us that there is an objective item that has its own nature in reality, asserting truth in an objective reality without the subjective knowing of that item to interfere. This axiom is the reason that biology, physics, and math are not in opposition to language, art, and music - there is a tacit understanding that there is the object and there is the experience of that object, and that they are separate.
Jean Paul Sartre noted that coming to this truth - that humans are confronted with stark objective truth behind the eyes of subjective experience. This epiphany of realizing the truth of existence in the human experience is painful and horrifying, but necessary for realizing absolute human freedom. After all, Sartre said that coming to know objective truth is a type of "being" that is categorically human in ways that "being" is not, referring to your experience of objective truth without a conscious experience of "what is" despite yourselfPost too long. Click here to view the full text.