Understanding existentialism is often difficult, often because its ideas conflict with other major trends in the thought of western and eastern philosophies alike. Many people consider existentialism to be a dark and pessimistic philosophy, void of hope. However, the opinions of existentialist thinkers were often optimistic about the future of human beings.

Existentialism can also be difficult to understand because it does not consist of a specific dogma, or a set of metaphysical claims. Existentialism is not a definitive claim about the world or the people in it. It is marked, instead, by a set of themes about the human condition and the struggles and freedoms that humans must endure, or perhaps embrace.

Despite the various and often conflicting views held by many existentialist philosophers, there are several main concepts of existentialism that are present in virtually all their works:

Sentient beings, especially humans, have free will.

Humans are responsible for the consequences of their decisions.

Extremely few, if any, decisions are void of negative consequence.

Even when part of a group, each person acts and decides as an individual, and is accountable as such.

The world is indifferent towards humanity.

The definition of existentialism is often hard to pin down, as there are conflicting views within existentialist thought, variations upon the ideas, and a number of so-called existentialists who rejected the title.

Perhaps the central feature of existentialism that can be seen in these points is the focus on the individual. Existentialists reject the idea that there is a fundamentally true human nature. Instead, they point out that those who seek to understand human nature undervalue the individual. The individual is free, as Sartre says, “radically free”. The individual can shape its own life and defy its so-called nature. The individual makes decisions and bears the responsibility for its actions alone.

Existentialism is a philosophy of the individual and its struggle through life — a focus on the subjective life that we all actually live, rather than a search for objective truths external to us.