Viktor Frankl was an Austrian neurologist, psychiatrist, philosopher, author, and Holocaust survivor. He is best known for his book "Man's Search for Meaning", in which he describes his experiences in Nazi concentration camps and his theory of logotherapy.

Frankl argues that humans are motivated by the search for meaning, and that this search is the primary driving force behind human behavior. He believes that when people find meaning in their lives, they are able to overcome adversity and live fulfilling lives.

Frankl argues that meaning is subjective, in the sense that it is unique to each individual and cannot be imposed from the outside. Purpose, on the other hand, is objective, in the sense that it is something that exists independently of the individual and can be discovered through reason.

Frankl argues that work, love, and creativity are the three primary sources of meaning in life. Work is meaningful because it allows us to contribute to society and to make a difference in the world. Love is meaningful because it allows us to connect with others and to experience intimacy. Creativity is meaningful because it allows us to express ourselves and to make something new.

Frankl argues that suffering can help us to find meaning in life by forcing us to confront our own mortality and to question the meaning of our existence. When we suffer, we are forced to ask ourselves what is truly important in life and what we are willing to live and die for.

Frankl argues that the meaning of life is not something that can be found outside of ourselves. It is something that we must create for ourselves, by living our lives in a meaningful way. This means finding meaning in our work, our relationships, and our creative endeavors.

Existentialism is the belief that life is meaningless because there is no objective meaning or purpose to existence. Nihilism is the belief that life is meaningless because there is no objective meaning or purpose to existence, and that this lack of meaning is a source of suffering.

Nietzsche's main thesis is that God is dead, and that this has profound implications for human existence. He argues that the death of God means that there is no longer any objective meaning or purpose to life, and that humans are now free to create their own values and meanings.

The Übermensch is Nietzsche's ideal human being, one who has overcome nihilism and embraced the will to power. The Übermensch is strong, independent, and creative, and is not afraid to live life on his or her own terms.

The will to power is Nietzsche's term for the driving force behind human behavior. He argues that humans are motivated by the desire to create something new, to overcome obstacles, and to achieve their goals. The will to power is not simply a desire for power over others, but a desire for power over oneself and one's circumstances.

Eternal recurrence is Nietzsche's idea that everything that has happened will happen again, forever. He argues that this is the ultimate test of a person's character, because it forces them to confront the meaninglessness of existence and to decide whether or not they are willing to live life anyway.

Camus' main thesis is that life is absurd, because there is no objective meaning or purpose to existence. He argues that this absurdity is a source of suffering, but that it can also be a source of liberation. When we accept the absurdity of life, we are free to create our own meanings and values.

Camus argues that the meaning of life is not something that can be found outside of ourselves. It is something that we must create for ourselves, by living our lives in a meaningful way. This means accepting the absurdity of life and creating our own meanings and values.

Sartre's existentialism is more focused on the individual, and on the individual's freedom and responsibility. Heidegger's existentialism is more focused on the world, and on the world's meaning and purpose.

Heidegger's main thesis is that being is the only thing that is. He argues that everything else, including the world and the individual, is a derivative of being. Being is the ultimate reality, and it is the source of all meaning and purpose.