The philosopher most impacting the film, The Unbearable Lightness of Being, is Friedrich Nietzsche, a German philosopher (1844-1900) who challenged his contemporary culture with his own ideas of morality, religion and will power; in particular the popular (and still today) idea that god is required to bring about certain modes of behavior.
This film explores Nietzsche's ideas especially one of eternal return. In his book, Kundera writes: "If every second of our lives recurs an infinite number of times, we are nailed to eternity as Jesus Christ was nailed to the cross. It is a terrifying prospect. In the world of eternal return the weight of unbearable responsibility lies heavy on every mood we make. Nietzsche called this concept of eternal return the heaviest of burdens. If eternal return is the heaviest of burdens, then our lives stand out against it in all their possible lightness.
"The heaviest of burdens crushes us, we sink beneath it, it pins us to the ground. But in the love poetry of every age, the woman longs to be weighed down by the man’s body. The heaviest of burdens is therefore simultaneously an image of life’s most intense fulfillment. The heavier the burden, the closer our lives come to the earth, the more real and truthful they become.
"Conversely, the absolute absence of a burden causes man to be lighter than air, to soar into the heights, take leave of the earth and his earthly being, and become only half real, his movements as free as they are insignificant.
"What then shall we choose? Weight or lightness?"
The Unbearable Lightness of Being as a film is not so weighty as it can not be enjoyed without looking at the philosophy underpinning it; but if you want to go deeper, than you can look at the various lifestyles as they are portrayed to see where choices lead. It is not suggesting punishment as a natural outcome of going against some godly set of rules, but rather of natural consequences.
Basically, as I saw it, the underlying theme is do the best we can do is lead a life that gives joy on the basic levels, which often comes through simple things and purposes; but despite what we do, fate may step in, not a directed fate but pure randomness where it all changes in an instant. This philosophy encourages us to both look at the result of reason but also not judge, when we see things turn out badly, that someone must have displeased god or done something wrong.
Sometimes despite natural consequences, fate steps in and in ways that relate to absolutely nothing. This is life. Trying to find meaning in everything can not only drive us crazy but in the end get nowhere. Humans want there to be a magical system to give us control. It is our nature and whether we expect that to come through science or a god, we struggle for it.
Some say Nietzsche was the underlying philosopher underpinning Nazism but you can find a philosophy of any sort and distort its meaning for evil purposes.
Nietzsche suggests discipline is a key to a quality life. Interestingly, even though Tomas is undisciplined sexually, where it comes to his work and sense of personal responsibility in many things, he very much is disciplined. He was an excellent surgeon who took great joy in his work; but when he was forced to change that because of the occupation of the Soviets, he took equal joy in being an ordinary doctor; when that was taken away, he found it in window washing. He did that with whatever work he did.
And then there is that title. Exactly what is the unbearable lightness of being? One possibility is that lightness is unbearable to those who wish to oppress which can be political, religious, or even individuals in our life who are threatened by our lightness as they seek to put their burdens onto us to gain control. Lightness is then a challenge to darkness?