John Paul Sarte in his work, "Existentialism" insists that existence precedes essence... basically, a human will turn up and appear on the scene and only afterwards begin to define themselves. He explains that this ultimately means that humans have complete freedom and responsibility to determine ones own development through acts of will. Sarte would tweaks spider-man's famous quote to state that "with great FREEDOM, comes great responsibility." Sarte explains that "existentialism's first motivation is it to make every man aware of what he is and to make the full responsibility of his existence rest on him... this does not mean he is solely responsible for his own individuality, but that he is responsible for all men." Ultimately when you are deciding the person YOU want to become, you are, in a way deciding the ideal of what you think all other humans ought to become.
Yogic philosophy only clashes with existentialism because the yoga philosophy holds the belief that our essence precedes existence. These teachings believe that we are ultimately this divine creature that has a perfect essence, it is our responsibility to UNCOVER the essence that is already at our core. These two differing theories propose the same argument of, "which came first, the chicken or the egg?" Yoga teaches us that despite being divine (or even to borrow a line from the bible - "made in Gods own image") - outside influences, the piling on of stress and "baggage", getting caught up in superficial dilemmas and not taking enough time to reflect and recover we begin to move further and further away from our essence. We are so focused on just existing and churning the wheels to make life happen that we forget the most important part of life, which is aligning with our essential true nature. Yoga Sutra chapter 1:3 states that when one is in the state of yoga (union) then the seer becomes established in its essence. When we start to get pulled in all directions, we get detached from this wholeness, but when we centre ourselves establishing that connection between the mind, body and the soul, then we are pulled towards our intrinsic nature.
My favourite metaphor for Sarte's argument contrasted with Yogic Philosophy is that of a piece of a marble and the sculptor. For Sarte, a sculptor has an idea of what they want to create with a slab of marble prior to creating and takes great care and strong determination to ensure it comes out the way they desire. For the teachings in yoga, when a sculptor carves into marble, they are removing everything that it not the statue... he does not add anything on to create his piece of art, just the willingness to do the work. The art of revealing beauty lies in removing what conceals it.
Therefore it is not as though the yogic philosophy takes away your freedom or will to choose who you become, instead it highlights the need to do the necessary work to chisel away at everything that is not essence, not self.
Both theories agree that when growing and evolving as a human, we are to consider how our actions effect others. In yoga we call this ahimsa, or no harm. The way we live and act in this world has a ripple effect through all humanity. Part of yoga which translates to union, is to understand that we are all One. Whether it is existence preceding essence or essence preceding existence, I think we can all agree upon the fact that we are all trying to figure out what our role is on earth, what is our purpose and what brings meaning to this existence.
Whether you are uncovering your essence or developing one, what kind of a person are you sculpting?