Our Gemara on amud beis provides the text for the Havdalah blessing which includes giving thanks for not only the distinction between holy and profane, but also include distinction between lightness and darkness. Clearly, the havdalah blessing isn’t merely a farewell to Shabbos. Rather, it is a meditation about the importance of distinctions, and even the importance of things we would consider undesirable.
Let us give some thought to the idea of darkness. It is fair to say that almost every culture and religion sees darkness as symbolic for evil, chaos and lawlessness while light is symbolic for spirituality, goodness and order. It’s not hard to guess why, considering especially how dangerous nighttime was before an era of electric lights,.
We are tempted to say darkness is evil or bad. Likewise, we are further tempted to say that evil is, well, evil. However, this is where understanding the importance of distinctions allows for a more philosophical approach. Think about it, a world with only light and no darkness would be the same sightless and visionless world as a world entirely in the dark. Because without the contrast of dark and light there is no vision. Similarly, without the contrast of moral choice between good and evil there is no good. This is hard to absorb but we know it to be deeply true.
People throughout the ages have tried to answer why there is evil in the world, why bad things have to happen, and why do we have to die or get sick? One approach that is hard to emotionally accept but is likely closest to the truth is that in order for good things to exist there simply must be evil as well. In order to really experience life there must be death. Now of course, we would like G-d to somehow do us a favor and make an exception. We even know there must be evil, entropy, and material existence, while at the same time every now and then, we hope G-d can insert himself into our lives as a special favor and exempt us from those vicissitudes. In the words of Tevye, “Would it spoil some vast eternal plan if I were a wealthy man?“ The answer is, Tevye, I'm sorry, but actually it would. Life without loss, existence without entropy is not the way reality can work most of the time. By its very definition, to exist means to allow for non-existence.
If G-d would allow himself to take up space in this world it would overshadow and blot out everything in physical existence, and any physical act of significance or meaning. It is like a world filled with light which would make everybody blind. In order to physically exist, we must also be subject to death, sickness, decay and evil.
Imagine if you could be hooked up to a machine that would provide you with a never ending intravenous drip of the perfect drug. You would be in an uninterrupted state of pure ecstasy, without any withdrawal or crash. Computers and machines would maintain your physical and organic function so you could live forever in this bliss. If you could choose to be stuck on this machine forever or have a regular everyday life with its ups and downs, health and sickness and eventually death, what would YOU choose?