Of course, there are a lot of ways to answer this question. From a scientific perspective, we could make an evolutionary argument. The more (genetic) variation that exists among a population, the more robust that population is against changes and therefore the more likely that population is to survive. For example, if one day, all green fruits became poisonous, then anyone that only ate green fruits would die. If we lived in a city that only ate green fruits, we would all die. On the other hand, if some of us ate green fruits and some of us ate red fruits, then at least some of us would survive.
Or we could take a humanistic perspective, and say that our desire for variety is really an intrinsic motivation to find new things to improve ourselves. Variety means we are constantly trying new things, and new things carry with them the possibility of better things. Part of what makes us human is our natural curiosity and penchant for asking hard questions.
And, of course, we could make an existential argument, and say that our constant desire for new things is born out of a need to continually distract ourselves from the crushing reality of existence. We constantly delve into the unknown simply because it is not the known, because the known is intolerable. Therefore, we are forced into the only solace we have, which is the new and unexplored. From this perspective, the devil you know is so horrible that you would take any other devil.
All of these are perfectly valid arguments (note, I'm not necessarily agreeing or disagreeing with any of them; I'm simply stating that they are logically sound within their respective frameworks). But they are all arguments of insufficiency; that is, at some point, every argument in defense of variety makes a claim that what we have is not enough. These genetic traits can't cover every possibility, or this knowledge doesn't satisfy us completely, or that distraction isn't enough to keep us occupied forever. The bottom line is, nothing is ever enough.
But what if something were?
What if there were a truly perfect, robust genetic makeup? What if there were Something that could permanently quench our thirst for more? What if there were Something that could continue to intrigue, interest, and astound us, such that we never needed to find another Thing again?
First of all, if such a Thing does not sound appealing to you ("Where's the fun in that?" and other such trite arguments), then I invite you to reread the last paragraph, as what I am suggesting is, by definition, above such oppositions. Most likely you are thinking that such a Thing would be nice, but we have no guarantee that such a thing exists. But humor me for a second, and imagine that such a thing did exist. What would it look like? To truly satisfy us permanently, it would have to be infinite, else we would risk reaching its end. It would also have to be multifaceted, else we might find that no part of even its infinite nature interests us. But ultimately, it would have to be real. Fiction can only captivate us for so long. That's why those who spend their entire lives obsessing over nothing but fiction usually end up trying to drag their fantasies into the real world in some way, often with little success, and usually with some amount of scorn or disdain from others (LARPing is one example).
Of course, I believe that such a Thing does exist, and that it is infinite and multifaceted and, most importantly, that it is real. I also believe that many people never find this thing. In fact, most people spend most of their lives not even knowing that they are searching, or what they are searching for, or where to being searching for it. As C.S. Lewis wrote, "All that we call human history--money, poverty, ambition, war, prostitution, classes, empires, slavery--[is] the long terrible story of man trying to find something other than God which will make him happy." I would even dare to brand a liar anyone who claims to have found something other than God that satisfies all of the requirements laid out above. From my perspective, such an alternative simply cannot, does not, and will not exist.
I'll give here two common examples of such insufficient things - alcohol and mind-altering substances. In particular, I'm going to address drunkenness and psychedelic experiences as means of satisfying this innate craving, but I'm going to try to go about it in less than traditional way. Normally, people view both of these as means of escape. Pastors will preach from the pulpit how people who habitually get drunk are trying to escape their normal life, or how those who frequently seek to alter their consciousness with LSD, mushrooms, or other psychedelics are running away from a disparaging reality. However, I don't think these explanations account for all, or even most, of people's motivations.
Let's look at alcohol. What is the defining characteristic of being drunk? I think most would agree that it is a loss of inhibitions. Rather than thinking or worrying about whether something should be done, a drunk simply does it as soon as they think it. Note that the same ideas enter their head whether they are drunk or sober, but they only result in action in a drunk mind. The sober person's mind has an added layer of questioning, which we can call inhibitions or social pressures or conformity or whatever else we wish. I claim that it is this layer that people are seeking freedom from when they pursue drunkenness. They no longer have to worry about should or shoudn't. They can simply be "free" to act as they think. Now, I firmly believe that this is objectively preferable, and even better. In fact, I believe in heaven, we will all exist in this state of no longer worrying or even thinking about should and shouldn't. However, the difference is that alcohol gives this freedom without the sanctification offered by God. In a perfect state, we will no longer have to concern ourselves with should and shouldn't because we will already by purified of any desire or thought that would warrant such worrying. All of our thoughts, ideas, and actions will be unquestionably good. Alcohol gives this freedom, but without this context of purification.
Psychedelic drugs are even trickier, mainly because descriptions of various experiences are unspecific at best. Nevertheless, a few recurring themes that I've heard in such accounts are increased perception (e.g. being able to feel every rock beneath your feet when walking on a gravel driveway, or seeing "new" colors) and metaphysical or spiritual experiences (e.g. experiencing and partaking in the "creation of the world" whilst sitting on a couch, or seeing your whole life laid out like a path). While I cannot comment from expertise, I see no reason to completely discount these descriptions. As a believer in the "supernatural" myself, I don't find it absurd to think that someone might be able to encounter things different from normal, everyday human experiences. However, what is clear from the huge variety of these experiences is that they lack any foundation in objective truth or reality. That's why, no matter how brilliant of a philosopher they seem to be, most people who make a habit of these experiences tend to give off rather underwhelming first impressions. Their experienced simply do not translate into the reality in which the rest of us spend the bulk of our time. Hallucinogens and drugs may truly give a glimpse of the divine or supernatural, of the spiritual underpinnings of our physical world. But they do so without the foundation that only the true Divine can provide. Thus, once again, we see these things are merely misguided attempts to seek and find something that only God can provide.
The bottom line here is to never settle for insufficiency. As C.S. Lewis writes in The Weight of Glory,
"If we consider the unblushing promises of reward … promised in the Gospels, it would seem that our Lord finds our desires not too strong, but too weak. We are half-hearted creatures, fooling about with drink and sex and ambition when infinite joy is offered us, like an ignorant child who wants to go on making mud pies in a slum because he cannot imagine what is meant by the offer of a holiday at sea. We are far too easily pleased.”The most important thing we can learn in life is that what we see immediately before us is not enough. The minute we accept this fact by refusing to accept these lesser things, we have begun our search for true joy and happiness. And we can take heart that this search will never be in vain, for God promises in Matthew 7:7-8 "Ask, and it will be given to you; seek, and you will find; knock, and it will be opened to you. For everyone who asks receives, and the one who seeks finds, and to the one who knocks it will be opened."
