I’ve always associated thinking with feeling. I’ve always known that thinking makes me feel a certain way. I used to wonder if other people thought that way, felt that way. One of the great pleasures of getting to know the world and my fellow human beings a little better over the years has been learning that however idiosyncratic I may feel (or be) at any given time about my thinking and the emotions it brings, I am never really alone.

Those times I feel that the way I feel when I think is not unique … those are good times. Sometimes those times last a while. Sometimes they come in flashes. Either way, those times are truly meetings. Each of those moments is what Richard Linklater’s characters in Waking Life call a “holy moment.”

I remember those moments. I remember the moment Dr. Roman read us T. S. Eliot’s words describing the way the Renaissance poet John Donne felt when he thought (or what Eliot believed was true, given Donne’s poetry and other writings): “For Donne, a thought was an experience; it modified his sensibility.” Those words are just as thrilling (ah, there’s one feeling I’ll come back to at the end) today as they were when I first heard them, age 19. They suggest that thinking is not just detached, ethereal, or impractical. Thinking is an experience. It changes you. Thinking changes your mind, which means that thinking changes the way you think. As one neurologist put it in the title of his recent book, we human beings have a Brain That Changes Itself. It’s like that great Escher drawing of the two hands drawing themselves. It’s recursive, and gloriously so.

And then it turns out that interest, which is the brain reaching in and out to experience the glorious trails of wonder and puzzlement within and without its hard-boned boundaries, is an emotion. A knowledge emotion, like confusion and awe. Just thinking about that idea fills me with joy. I’m listening to Pandora (The Buckinghams channel, if you’re curious) as I type these words, just to keep my brain in the happy state that allows the joy of these ideas to permeate every axon, jump every synapse.

Thinking doesn’t always feel great, of course, even for someone like me who’s frankly besotted with it. Sometimes thinking is unpleasant, hard, regretful. When I worry, for example, I’m thinking about things that either a) make me anxious or b) consume me with an urgent set of problems, the way we say a dog “worries” a bone. Actually, now that I think about it (heh), “b” can feel unpleasantly focused sometimes, but other times it feels like good exercise. By contrast, I try to avoid the “a” variety of worry, sometimes with more success than others.

But leaving aside that unpleasantness, I believe there are other varieties of thinking that are pretty much unalloyed pleasure, though of different kinds. (Anyone who tells you that all pleasures are really the same needs to get out more.) Here’s a partial listing of my thinking pleasures.

Musing is a great relaxed pleasure as long as “a” worries don’t intrude. Musing is that state when the mind floats free, playing with associative trails the way a child plays with soap bubbles, balloons, or sticks in a brook. When musing gets very intense, it gets even dreamier, at least for me; it becomes a reverie, which to my ears is one of the loveliest words in the language, though obviously we borrowed it from the French. Not that there’s anything wrong with that.

Mulling is a somewhat more arduous pleasure. “Mulling” means thinking hard but without any single goal in mind. Mulling is like a great conversation that grows more intense by the moment, but without any agenda or “takeaway” that has to be agreed upon or accomplished. I once did a talk on mulling (the thinking kind, not the vintner variety), and because I had to do the talk, I ended up learning what it was I wanted to say. It came to me in the course of my research (see, there’s inquiry for you). I learned that the words “mull,” “meal,” and “muddle” were all related. Irresistible words. Alliterative, and nicely balanced between two monosyllables and one disyllable. Best of all, they gave me the grand finale that I hoped would also give the audience something to mull over as they thought about my talk on thinking: I concluded that “mulling” was what we did to make a “muddle” into a “meal.” Ok, two disyllables there, but I’m an amateur poet only.

Worrying (“b” type), musing, mulling: all are pleasures, though all feel different. But for the tip-top pleasure, the one that keeps me moving through uncertainty and courting more (heaven knows–for a fact–that there’s no lack of uncertainty in life and in this weary world), is the feeling I get when an idea comes to me. When that idea arrives, it sometimes feels like moving through a door to see a splendid sunlit landscape on the other side. Sometimes it feels like I’ve spotted a long-lost friend while music plays in the most exquisite foreign land I’ve ever visited (the choice of which, music and land and friend, would depend on the day). Sometimes it feels the way I felt when I saw my newborn children and the exhausted joy in their mother’s eyes. Sometimes I get the feeling and I don’t know why, because some part of my brain has registered the insight, has felt the charge of the connection, before my prefrontal cortex has had a chance to say to itself, “Whoa! I see!”

Roger Penrose describes this last sensation so perfectly that I leave the last word in this post to him, as given to us by the superb immortal filmmaker Errol Morris: