This intro to philosophical discussion takes on several basic philosophical questions. Nagel walks the reader through several common avenues of philosophical analysis until leaving the reader with several questions to answer for themselves. In this review, I will take on some of Nagel's questions.
How do we know anything?
Solipsism posits that the only thing that exists is our minds. But we don't know that. We know that it is all we can experience, but not all that is. Skepticism doubts that any external world exists. But again, there is no way to know that. Is it meaningful to believe that only one's own mind exists? No. Is it meaningful to assume that the world outside is something completely different than what it seems to be? Possibly.
We know that our sense organs are quite different than many other animals. However, we all seem to be measuring the aspects of the environment that we need to in order to survive in our bodies. Each type of body is adapted to survive in a niche of the environment. We can make a conjecture that the external world is the sum of all the senses of all the organisms that exist. But as a human, we can still only experience a sliver.
If it's possible that my mind is all that exists or that the external world is something drastically different than what I perceive, I have no way of proving it to myself or others, so it's a waste of time and energy to hold that position. I also can't prove that anything DOES exist outside my mind, so is it alright to go on believing in the external world anyway? The definition of "alright" is up to each one of us and I say it's alright. Regardless, I can understand that as a human, society and culture are constructed by tacit agreements or other agreements among humans. I don't have to believe in an external world, but I can believe in the consequences of actions that come from my own mind as I perceive it. The consequences of not believing in an external world can have severe consequences. If I jump off a cliff I will find out quickly whether the external world exists or not. It's not a wager most people will take. It's likely not just alright to keep believing in an external world, but necessary to continue to experience my mind. In fact, if my mind is all that exists, then my mind tells me quite often about dangers and things I should do to avoid my mind ending. Indeed, if the external world doesn't exist, since my mind seems to want me to believe quite strongly that an external world full of dangers exists, then it's quite all right to continue to believe in it.
Other Minds
How do you know that all the beings around you aren't just elaborate robots? Instinct isn't knowledge. There isn't any way for one to know that any other being has any inner experiences at all.
What can you really know about the conscious life in this world beyond the fact that you have a conscious mind? You can't really know at all. There is no way to know what people, organisms, and inanimate objects experience. However, from reading books and listening to people, one encounters thoughts which very much appear to be the result of self-reflection and inner reflection, which takes place as a result of consciousness. While the existence of books and speeches that seem to be encoded with inner reflection enter my sensory world quite often, this is still no evidence. Nevertheless, that these thoughts appear from others' mouths and hands compels one to lean more on the side of other humans having consciousness and an inner world.
Is it possible that there might be much less conscious life than you assume, or much more? Just as some stars shine more brightly than others, it does seem that some lifeforms have much more consciousness than others, and as a result, some creatures and objects have much less consciousness. This isn't evidence, but merely a statement based upon the distribution of characteristics within the universe concerning, height, weight, intelligence, life span, size, and so on. Within species, there appears to be a wide-range of possible manifestations of characteristics. Consciousness is likely similar.
The Mind-Body Problem
Is the mind purely physical or is there some spiritual component? Nagel talks about the taste of chocolate and how it is distinct from the chemical and electrical signals in the brain. A symphony orchestra plays music, but is the experience of music something non-physical? If the experiences we have as humans require a spirit separate from the physical aspects, why are there physical aspects at all? If the spirit requires the physical components of neurons and eyeballs, then the spirit is dependent upon the physical and thus physical itself. We can reduce this problem by taking various disabilities into account. Are blind people lacking in spirit? Are deaf people lacking in spirit? If not, then the physical experiences we have, have nothing to do with spirit at all and this includes our thoughts which are also just neurons firing with moods modulated by chemicals such as dopamine and serotonin.
The other way of saying that everything is physical, is also to say that everything is spiritual. Why can't physicalism be turned around and stated as if there is no dualism, then everything is spiritual even if it has a physical aspect to it. This seems to be a stretch though, since there is quite a lot of pain, suffering, disease, abuse, neglect, boredom, forgetfulness, and so on. How can spirit be forgetful? If everything is spiritual, what is the purpose of acquiring decades of experience and wisdom only for dementia to erase it all? A physical explanation makes far more sense where our bodies are here for the purpose of sexual reproduction (a physical process) to pass on physical genes and then be done with it. Everything about our nature as humans, points toward our bodies needing to be useful long enough to have and raise a few children and then the world no longer needs us around. Regardless of how each person experiences our inner world, we can objectively see how the environment treats other organisms and that physical processes wear down and destroy everything about each being, including the parts that some ascribe to being spiritual.
Free Will
Is everything, including our thoughts, and every action we take in every circumstance inevitable, or determined before it happens? Existentialists believe that we aren't determined. It is up to each of us to discover meaning in our lives and work to become the people that we want to be. Even if everything is determined, it seems clear that it is determined that most people will not believe that everything is determined simply because of the psychological jail that is created as a result. If everyone believed that everything is determined people would not feel guilt, remorse, hope, responsibility, and so on. The fact that almost everyone feels all of those things is proof enough that if the entire universe unfolds in a determined way, that unfolding includes humans believing that their actions, thoughts, and feelings are not determined. It seems as if most of life is determined though: who we are born to, the times we are born into, the environment around us, geopolitics, and the economy. However, in each moment, we have several options, even if they are very small. Even the existence if a minuscule percentage of choices still constitutes choice. So, while we are not absolutely determined, it appears our free will is considerably small.
Death and the Meaning of Life
Thomas Nagel ends the book by taking on two topics: death and the meaning of life. He mainly contrasts religious belief which accepts an afterlife and the worship of a god at face value without question. Of course, these conclusions aren't acceptable for a philosopher as there is no evidence of, but plenty of evidence against this position being tenable. Here is where Nagel introduces humor, and suggests that if one is able to take oneself not very seriously, then death and the meaning of life aren't such bitter pills to swallow. It's only when we cling to these concepts with such seriousness that we feel we must have a purpose, that we must live on forever, that these problems become too hard to handle. I have to agree that if there is an antidote for existential angst, humor must be an ingredient.
An Eastern take
After asking all of these questions and spending all this time thinking about what is and what isn't, there is still another valid philosophical angle. This one comes from Buddhism. In Buddhism, spending time on questions like this is considered a waste. Since we know that we cannot know, Buddhists say that time should only be spent on working on the present moment. Buddhism isn't interested in metaphysical speculation, only in the pursuit of conquering his own mind without wasting time on unimportant and unnecessary philosophical puzzles. Zen Buddhism is concerned with what is going on around us and the simple, practical matters about life. This is summed up in this tale:
A monk told Joshu, "I have just entered the monastery. Please teach me."
Joshu asked, "Have you eaten your rice porridge?"
The monk replied, "I have eaten.""
Joshu said, "Then you had better wash your bowl."
At that moment the monk was enlightened.
From the perspective of Zen, all of these questions are a waste of time and only get in the way of our development.
But we can ask many questions about the Buddhist perspective as well. Does Buddhism have any motivation to encourage its followers not to ask questions? Just because someone who was called "enlightened" said some things, does that mean they should be listened to without question?
All religions draw lines in the sand and encourage followers to stay within the boundaries of dogma. Buddhism is no different. Not only does Buddhism encourage followers to deny their desires and urges, but also to deny themselves the pondering of metaphilosophical questions. Where's the fun in that?