How do you learn to think? Let's start with how you don't learn to think. A study by a team of researchers at Stanford came out a couple of months ago. The investigators wanted to figure out how today's college students were able to multitask so much more effectively than adults. How do they manage to do it, the researchers asked? The answer, they discovered—and this is by no means what they expected—is that they don't. The enhanced cognitive abilities the investigators expected to find, the mental faculties that enable people to multitask effectively, were simply not there. In other words, people do not multitask effectively. And here's the really surprising finding: the more people multitask, the worse they are, not just at other mental abilities, but at multitasking itself.

One thing that made the study different from others is that the researchers didn't test people's cognitive functions while they were multitasking. They separated the subject group into high multitaskers and low multitaskers and used a different set of tests to measure the kinds of cognitive abilities involved in multitasking. They found that in every case the high multitaskers scored worse. They were worse at distinguishing between relevant and irrelevant information and ignoring the latter. In other words, they were more distractible. They were worse at what you might call "mental filing": keeping information in the right conceptual boxes and being able to retrieve it quickly. In other words, their minds were more disorganized. And they were even worse at the very thing that defines multitasking itself: switching between tasks.

Multitasking, in short, is not only not thinking, it impairs your ability to think. Thinking means concentrating on one thing long enough to develop an idea about it. Not learning other people's ideas, or memorizing a body of information, however much those may sometimes be useful. Developing your own ideas. In short, thinking for yourself. You simply cannot do that in bursts of 20 seconds at a time, constantly interrupted by Facebook messages or Twitter tweets, or fiddling with your iPod, or watching something on YouTube.

I find for myself that my first thought is never my best thought. My first thought is always someone else's; it's always what I've already heard about the subject, always the conventional wisdom. It's only by concentrating, sticking to the question, being patient, letting all the parts of my mind come into play, that I arrive at an original idea. By giving my brain a chance to make associations, draw connections, take me by surprise. And often even that idea doesn't turn out to be very good. I need time to think about it, too, to make mistakes and recognize them, to make false starts and correct them, to outlast my impulses, to defeat my desire to declare the job done and move on to the next thing.

... You do your best thinking by slowing down and concentrating.

Now that's the third time I've used that word, concentrating. Concentrating, focusing. You can just as easily consider this lecture to be about concentration as about solitude. Think about what the word means. It means gathering yourself together into a single point rather than letting yourself be dispersed everywhere into a cloud of electronic and social input. It seems to me that Facebook and Twitter and YouTube—and just so you don't think this is a generational thing, TV and radio and magazines and even newspapers, too—are all ultimately just an elaborate excuse to run away from yourself. To avoid the difficult and troubling questions that being human throws in your way. Am I doing the right thing with my life? Do I believe the things I was taught as a child? What do the words I live by—words like duty, honor, and country—really mean? Am I happy?

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So it's perfectly natural to have doubts, or questions, or even just difficulties. The question is, what do you do with them? Do you suppress them, do you distract yourself from them, do you pretend they don't exist? Or do you confront them directly, honestly, courageously? If you decide to do so, you will find that the answers to these dilemmas are not to be found on Twitter or Comedy Central or even in The New York Times. They can only be found within—without distractions, without peer pressure, in solitude.

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These are truly formidable dilemmas, more so than most other people will ever have to face in their lives, let alone when they're 23. The time to start preparing yourself for them is now. And the way to do it is by thinking through these issues for yourself—morality, mortality, honor—so you will have the strength to deal with them when they arise. Waiting until you have to confront them in practice would be like waiting for your first firefight to learn how to shoot your weapon. Once the situation is upon you, it's too late. You have to be prepared in advance. You need to know, already, who you are and what you believe: not what the Army believes, not what your peers believe (that may be exactly the problem), but what you believe.