Here’s something you’ll know if you’ve ever sat through a boring lecture: sometimes your mind simply goes wherever it will. Thoughts of different kinds come to you, one after the other, linked by mere association. At one moment you’re daydreaming about your new puppy; in the next, you suddenly recall that “W.H.O. let the dogs out”tweet; moments after, you sit through a mental rendition of the classicBaha Men song; and from there, you have flashes of your misspent youth. When your thoughts freely transition one to the next in this way, we sometimes say your mind is ‘wandering.’

但这并不是你的想法得以延续的唯一方式。与此形成对比的是，在一段时间内，你的精神高度集中——比如，当你在努力计算填字游戏中12 Down的答案时。在这种情况下，你的大脑不会想去哪就去哪。在这种情况下，你的思想停留在一个主题上，从多个角度接近它;你的思想系列有一个更有限的路径。您可能会考虑一个选项来填写这个单词(例如，FROTH)，然后认为FDR可能会进入12 Across，但ANGST不适合13 Down，因为它需要这样做，所以您拒绝FROTH作为12 Down的答案，并考虑BROTH，等等。

So far we’ve just marked one clear—but somewhat superficial—difference between mind-wandering and crossword-solving. In mind-wandering, you can take a mental walk through various topics that are only loosely connected by association. In crossword-solving, on the other hand, your thoughts are focused on one specific topic. What explains this superficial difference?

What explains this superficial difference is a deeper difference between these two cases. It’s the difference betweennot doing much of anything at allanddoing somethingin thought: engaging in some mentalaction.

我所描述的走神是一种思维模式，在这种思维模式下，你无法控制自己的思想主题。By contrast, in solving a crossword puzzle you’re engaged in a specificaction: you are solving the 12 Down clue. You might do it with a particular purpose (e.g. the purpose of solving the whole crossword, or the purpose of having fun), and you might use specific strategies to carry it out (e.g. thinking of all the words you know that end in -OTH). It requires effort and concentration.

Importantly, when you’re solving the 12 Down clue, youcontrolthe topics of your thoughts. You couldn’t really act if you didn’t havesomecontrol; if some unseen or outside forces completely determined the contents and flow of your thoughts, there wouldn’t be any room for you to play a role. So part of what it is to say thatsolving the clue for 12 Downis anaction是说你在这里行使控制——特别是控制你的思想。

This explains why your thoughts don’t ‘wander’ through different topics in this case. Part of the control you’re exercising is control over what you are thinking about. If you were to start thinking about something else in the crossword case, you would snap back your attention to the task at hand. Not so in the case of mind-wandering: there, you aren’t restricting your attention at all, but just sitting idly by while it flits from one topic to another.

This raises another natural question: what does control involve here?

In this case, as in many others, acting withcontrolseems to involverepresentingwhat you’re trying to do. In other words, you have an idea of what you’re trying to do. Here, that idea represents what you are trying to as “solving the clue for 12 Down.” This idea of what you’re trying to do is central to control, because it helps you snap back on task when (e.g.) your thoughts begin to drift toward Baha Men music again. If you didn’tkeep in mindany idea of what you were trying to do, when those catchy lines slipped into your stream of consciousness, you would simply forget—and thereby abandon—your prior mental task.

If we accept that (i) mental action requires control and (ii) control requires an idea of what you’re trying to do, we come to a striking conclusion: when you’re engaged inmentalaction, we can describe both the stream of thought you are engaged in, andthe way you’re thinking of what you’re doing, as two crucial aspects of your mental life and its significance for you. If I interrupted you during your thoughts about 12 Down and askedwhatyou were thinking, you might just report the pieces of language that show up in your thoughts (“FROTH… BROTH… CLOTH…”). After all, words are at the center of your focus when you’re completing a crossword. But this isn’t mere idle free association; at the same time, you understandwhat you’re doing要想了解你此时此刻的精神生活，也需要提到这一点。我可能会问你:“你为什么会这么想?你可能会说:“哦，我认为它们是12下的答案。”

To use a metaphor, we might say that there are twolayersto your thought when you are engaged in mental action: there’s the content of your thoughts, orwhatyou’re thinking—FROTH, then BROTH, then CLOTH—and then there’s the layer of self-understanding that represents what you are trying to do all along, as “figuring out the answer to 12 Down.”

This is just one of the reasons that mental action matters in philosophy. When we describe a stream of thoughts as part of an ongoingaction, we thereby imply that there’s an overarching structure to your thought that controls its direction. You do this by keeping in mind what you’re trying to do. And that implies that—unlike in mind-wandering—the significance of each of your individual thoughts (e.g. the thought of “FROTH”) is not just local, a little island on which your attention has alighted for a brief pause. The significance to you is much greater than that. Each of your thoughts might have some local content (“FROTH” or “BROTH” or “CLOTH”) but you also see it as playing a role in the larger mental project in which you are engaged.