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 classic Baha 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.’ 

But that’s not the only way your thoughts can proceed. Contrast this meandering with a period of tight mental focus—say, when you’re hard at work figuring out the answer to 12 Down in a crossword puzzle. In this case, your mind doesn’t just go anywhere it likes. In this case, your thoughts stay on one topic, approaching it from several angles; the series of your thoughts has a more circumscribed path. You might consider one option for filling the word out (say, FROTH), and then think FDR might go into 12 Across, but then ANGST wouldn’t fit in 13 Down, as it needs to do, so then you reject FROTH as the answer to 12 Down and consider BROTH, and so on. 

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 between not doing much of anything at all and doing something in thought: engaging in some mental action.  

The kind of mind-wandering I described is a mode of thought in which you don’t control the topics of your thoughts. By contrast, in solving a crossword puzzle you’re engaged in a specific action: 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, you control the topics of your thoughts. You couldn’t really act if you didn’t have some control; 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 that solving the clue for 12 Down is an action is to say that you are exercising control here—in particular, in control over your thoughts.

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 with control seems to involve representing what 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’t keep in mind any 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 in mental action, we can describe both the stream of thought you are engaged in, and the 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 asked what you 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 understand what you’re doing and a full story of your mental life at this moment would need to mention this as well. I might ask you: “Why are you thinking those things?” and you might say: “oh, I’m considering them as answers to 12 Down.”

To use a metaphor, we might say that there are two layers to your thought when you are engaged in mental action: there’s the content of your thoughts, or what you’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 ongoing action, 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.