John Stewart Mill was the son of a great classical utilitarian. He was taught that happiness could be measured on a one-dimensional scale from pain to pleasure. Since he was only one of many millions of human beings, he should focus on helping others to be happy by serving them directly and by reforming laws and policies to maximize happiness. Happiness was a simple quantity determined by circumstances beyond the individual.

As a young man, Mill became deeply depressed. He asked himself:

“Suppose that all your objects in life were realized; that all the changes in institutions and opinions which you are looking forward to, could be completely effected at this very instant: would this be a great joy and happiness to you?” And an irrepressible self-consciousness distinctly answered, “No!” At this my heart sank within me: the whole foundation on which my life was constructed fell down. All my happiness was to have been found in the continual pursuit of this end. The end had ceased to charm, and how could there ever again be any interest in the means? I seemed to have nothing left to live for.

Mill realized that other people could not make him happy, and the same was true of everyone else. Each person had to pay attention to her own wellbeing or everyone would be miserable. One reason is that we do not fall on a single spectrum from agony to ecstasy. Instead, we experience a heterogeneous batch of emotions (joy, peace, pain, acceptance, delight, equanimity, and many more) that may be in tension with each other. Mill’s ultimate response was to develop a richer philosophy in which the inner life regained its independent standing and was no longer a mere outcome of justice. “The important change which my opinions at this time underwent, was that I, for the first time, gave its proper place, among the prime necessities of human well-being, to the internal culture of the individual. I ceased to attach almost exclusive importance to the ordering of outward circumstances.”

This kind of reflection recalls the intrinsic value–the beauty, complexity, and richness–of inner life itself. Introspection counters an avoidable modern tendency to disenchant the self.

Many centuries ago, the world seemed thoroughly enchanted. There were spirits, angels, or demons in the air, the forest, the water, and everywhere else. It seemed natural that there should also be a spirit inside each of us that was similarly invisible, unpredictable, powerful, and precious.

Natural science has not demonstrated that the only real things are visible and predictable. On the contrary, natural science has discovered quarks and bosons, forces and dimensions. It had yielded a world full of strange and heterogeneous objects. But natural science does presume (rather than discover) that every true statement is about something that one can demonstrate experimentally. As natural science has progressed, the enchanted world has shrunk: we now know that hot and cold fronts rather than demons cause storms, and bacteria and viruses rather than witches cause disease.

An object inside us that we might call a soul, a self, or a will seems likely to disappear for the same reasons. After all, a soul can never be observed or experimentally verified. And science is building an alternative story about networks of neurons that fire (because of forces acting on them) and cause mental states such as desire and will. In turn, these networks of neurons evolved over many millions of years to make species like ours more fit to survive. The implication is that human beings are ultimately just complicated machines, and an experience like freedom of the will is an illusion. Our thinking belongs to the same network of cause-and-effect that explains why a computer opens an application when you push a button, or a tree sprouts a leaf when the sun shines on it.

The premises seem correct, but the conclusion does not follow. Natural science may explain why mental states occur. It cannot not explain what those states are. By analogy: biology explains why most leaves look green, but it wouldn’t convey to a truly color-blind person what green looks like. Likewise, a conscious person actually experiences will, choice, and a host of other complex mental states. To say what will is, one must describe it closely and insightfully from the perspective of the person who wills something. Under close inspection, a simple thing like “will” refracts into many related emotions and beliefs. One must address questions like these: What does it feel like to want something? Can you want it and not want it at the same time? Does wanting an object feel the same as wanting a person? How does will relate to love? To happiness? What thoughts and mental practices enhance and constrain will? What forms of willing are good and which are bad?

Such introspective questions are appropriate even in a world in which natural science works just as well as advertised. If you want to know why human beings think, it’s appropriate to turn to neuroscience and evolutionary biology. But if you want to know what thought is, you must attend to thinking. Even more so, if you want to decide which thoughts are good, you must evaluate the complex, subtle, mysterious world of your own consciousness.

Both the Talmud and the Qur’an propose that to murder one person is to destroy a whole world, and to save a life is to save a whole world. Perhaps those passages reflect a recognition that each human consciousness is an immense accumulation of experience. The whole universe of which I am aware (from distant galaxies to microscopic organisms swimming in a drop of water) is all in my head. My mind contains not one thing but many things connected by a whole network of relations. And each of these things carries value. Consciousness thus requires and rewards exploration. Montaigne wrote: 

For, as Pliny says, each person is a very good lesson to himself, provided he has the audacity to look from up close. This [the book of Essays] is not my teaching, it is my studying; it is not a lesson for anyone else, but for myself. What helps me just might help another. … It is a tricky business, and harder than it seems, to follow such a wandering quarry as our own spirit, to penetrate its deep darknesses and inner folds. …This is a new and extraordinary pastime that withdraws us from the typical occupations of the world, indeed, even from the most commendable activities. For many years now, my thoughts have had no object but myself; I investigate and study nothing but me, and if I study something else, I immediately apply it to myself–or (better put) within myself. … My vocation and my art is to live (ii.6).