Neurocritic asks a great question here, neatly provoking that which he would have defined – thought. What is thought, and what are individual thoughts? He quotes reports that we have an estimated 70,000 thoughts a day and justly asks how on earth anyone knows. How can you count thoughts?

Well, we like a challenge round here, so what is a thought? I’m going to lay into this one without showing all my working (this is after all a blog post, not a treatise), but I hope to make sense intermittently. I will start by laying it down axiomatically that a thought is about or of something. In philosophical language, it has intentionality. I include perceptions as thoughts, though more often when we mention thoughts we have in mind thoughts about distant, remembered or possible things rather than ones that are currently present to our senses. We may also have in mind thoughts about perceptions or thoughts about other thoughts – in the jargon, higher-order thoughts.

Now I believe we can say three things about a thought at different levels of description. At an intuitive level, it has content. At a psychological level it is an act of recognition; recognition of the thing that forms the content. And at a neural level it is a pattern of activity reliably correlated with the perception, recollection, or consideration of the thing that forms the content; recognition is exactly this chiming of neural patterns with things (What exactly do I mean by ‘chiming of neural patterns’? No time for that now, move along please!). Note that while a given pattern of neural activity always correlates with one thought about one thing, there will be many other patterns of neural activity that correlate with slightly different thoughts about that same thing – that thing in different contexts or from different aspects. A thought is not uniquely identifiable by the thing it is about (we could develop a theory of broader content which would uniquely identify each thought, but that would have weird consequences so let’s not). Note also that these ‘things’ I speak of may be imaginary or abstract entities as well as concrete physical objects: there are a lot of problems connected with that which I will ignore here.

So what is one thought? It’s pretty clear intuitively that a thought may be part of a sequence which itself would also normally be regarded as a thought. If I think about going to make a cup of tea I may be thinking of putting the kettle on, warming the pot, measuring out the tea, and so on; I’ve had several thoughts in one way but in another the sequence only amounts to a thought about making tea. I may also think about complex things; when I think of the teapot I think of handle, spout, and so on. These cases are different in some respects, though in my view they use the same mechanism of linking objects of thought by recognising an over-arching entity that includes them. This linkage by moving up and down between recognition of larger and smaller entities is in my view what binds a train of thought together. Sitting here I perceive a small sensation of thirst, which I recognise as a typical initial stage of the larger idea of having a drink. One recognisable part of having a drink may be making the tea, part of which in turn involves the recognisable actions of standing up, going to the kitchen… and so on. However, great care must be taken here to distinguish between the things a thought contains and the things it implies. If we allow implication then every thought about a cup of tea implies an indefinitely expanding set of background ideas and every thought has infinite content.

Nevertheless, the fact that sequences can be amalgamated suggests that there is no largest possible thought. We can go on adding more elements. There’s a strong analogy here with the formation of sentences when speaking or writing. A thought or a sentence tends to run to a natural conclusion after a while, but this seems to arise partly because we run out of mental steam, and partly because short thoughts and short sentences are more manageable and can together do anything that longer ones can do. In principle a sentence could go on indefinitely, and so could a thought. Indeed, since the thread of relevance is weakened but not (we hope) lost at each junction between sentences or thoughts, we can perhaps regard whole passages of prose as embodying a single complex thought. The Decline and Fall of the Roman Empire is arguably a single massively complicated thought that emerged from Gibbon’s brain over an unusually extended period, having first sprung to mind as he ‘sat musing amidst the ruins of the Capitol, while the barefoot friars were singing vespers in the Temple of Jupiter’.

Parenthetically I throw in the speculation that grammatical sentence structure loosely mirrors the structure of thought; perhaps particular real world grammars emerge from the regular bashing together of people’s individual mental thought structures, with all the variable compromise and conventionaljsation that that would involve.

Is there a smallest possible thought? If we can go on putting thoughts together indefinitely, like more and more complex molecules, is there a level at which we get down to thoughts like atoms, incapable of further division without destruction?

As we enter this territory, we walk among the largely forgotten ruins of some grand projects of the past. People as clever as Leibniz once thought we might manage to define a set of semantic primitives, basic elements out of which all thoughts must be built. The idea, intuitively, was roughly that we could take the dictionary and define each word in terms of simpler ones; then define the words in the definitions in ones that were simpler still, until we boiled everything down to a handful of basics which we sort of expected to be words encapsulating elementary concepts of physics, ethics, maths, and so on.

Of course, it didn’t work. It turns out that the process of definition is not analytical but expository. At the bottom level our primitives turn out to contain concepts from higher layers; the universe by transcendence and slippery lamination eludes comprehensive categorisation. As Borges said:

It is clear that there is no classification of the Universe that is not arbitrary and full of conjectures. The reason for this is very simple: we do not know what kind of thing the universe is. We can go further; we suspect that there is no universe in the organic, unifying sense of that ambitious word.

That doesn’t mean there is no smallest thought in some less ambitious sense. There may not be primitives, but to resurrect the analogy with language, there might be words.  If, as I believe, thoughts correlate with patterns of neural activity, it follows that although complex thoughts may arise from patterns that evolve over minutes or even years (like the unimaginably complex sequence of neural firing that generated Gibbon’s masterpiece), we could in principle look at a snapshot and have our instantaneous smallest thought.

It still isn’t necessarily the case that we could count atomic thoughts. It would depend whether the brain snaps smartly between one meaningful pattern and another, as indeed language does between words, or smooshes one pattern gradually into another. (One small qualification to that is that although written and mental words seem nicely separated,  in spoken language the sound tends to be very smooshy.) My guess is that it’s more like the former than the latter (it doesn’t feel as if thinking about tea morphs gradually into thinking about boiling water, more like a snappy shift from one to the other), but it is hard to be sure that that is always the case. In principle it’s a matter that could be illuminated or resolved by empirical research, though that would require a remarkable level of detailed observation. At any rate no-one has counted thoughts this way yet and perhaps they never will.


  1. 1. Lloyd says:

    Your paragraph about gradually smooshing reflects on my reflections that a thought is more than a perception. For me, reading brings this out in ways that writing would smoosh. For me, a “thought” is not a word, but at minimum, a phrase. The thought requires a separation of content. For example, I could look at the teapot and not have a separate thought about the handle, even though it would be within my perception of the pot.

  2. 2. Hunt says:

    Great post, well written and very “thoughtful”. Part of the discussion should include the possible categories of thought, sequential, free associative, etc. Even the possibility of the absence of thought should be considered, the separation of perception from thought, as contemplative purport to master. Either what we call “thought” includes subprocesses controlling these aspects, or thought is actually governed by higher “executive” cognitive functions. The idea being that thought is just one tool employed by the brain in specific circumstances, perhaps, say, to resolve possible world hypotheses with what actually exists, as determined by sensory input, prior thought captured in memory, and so on.

    I do think this is one primary function of thought, to resolve the cohort of possible worlds we all keep in mind into a single “best guess” of how the world is, for us. Some people are resolved in this process and some are maintain looser association, but for everyone, the product of thought must provide a worldview that makes some sense of the world (is not terrifying) when we walk out the front door.

  3. 3. SelfAwarePatterns says:

    “Thought” seems like one of those amorphous words. No matter how you define it, someone will probably find one or more examples of usage that violate that definition. Even simply saying it’s neural firing patterns encounters the difficulty that most people wouldn’t consider the brain’s autonomous functionality (such as regulating body temperature) to be thinking. And we often talk about acting “thoughtlessly” in a given situation, indicating that habitual or instinctive reactions usually fall outside the scope of what we mean by it.

    It seems to me that the most common intuitive meaning is imaginative scenario simulations, projections of what perceptions and emotions might be triggered if certain decisions or events happen. Humans enhance this ability with symbolic thought, including language, which allows us to add structure and extend these simulations far more than most animals. Although the simulation might be about what will happen in the next second if we’re closely attending to a real time situation.

    As to atomic thoughts, I agree it’s most likely an incoherent idea. Thoughts seem to be neural firing patterns which blur into each other. We can talk about an atomic unit of mental processing: such as maybe a single neuron firing, or the actions of particular proteins in synapses, but thoughts seem like higher order patterns where, unless far apart, the borders between them are arbitrary.

    But when we discuss our thoughts, we should remember that we’re not necessarily talking about the raw mental processing, but of what we metacognitively can perceive about that raw mental processing. That might sound overly pedantic, but consider how often someone’s friends can know their thoughts better than they themselves do. Which seems to open the question: what is the thought, the mental processing, or our perception of the mental processing? How can we know the difference?

  4. 4. arnold says:

    Differences come to us from comparisons, like comparing instinct, sensation, emotion and mentation–in biology…
    …Evolution provides comparisons for animals becoming human…and thought has already appeared in our evolution…

    Evolving, as we appear to be–then what is next…
    …I propose learning to respect our functioning as being part of a universal physical process that attracts observation…

  5. 5. Paul Topping says:

    The idea of counting thoughts is ill-conceived. Even though we don’t know how the brain works in detail, we are confident that it does process things in parallel. Even if thoughts aren’t “smooshed” together, it seems very difficult to imagine that “thoughts per second” has any real meaning.

    On the other hand, once we do know how the brain works in detail, we can surely come up with some kind of speed measurement but it is unlikely the unit will be “thought” but something more specific.

  6. 6. Jayarava says:

    I pretty much agree with your characterisation of thought.

    It is a very interesting thing to say that thought has “content” rather than, say, “being”. What is the ontology of content without being? If we chunk down a level we can see the thought instantiated by correlated neural patterns. But the patterns themselves are not the experience of having a thought. Reductionism fails, because going down levels destroys the higher level emergent phenomena we are interested in.

    Ancient Indian Buddhists contrasted experiences with real things. They understood that a mental object was unlike a physical object – a mental object is not located or extended in space. A a mental object does not move the way physical objects move. Though we do have experiences, a mental objects cannot be described in terms of existence or non-existence (at least in the usual sense of these words). In which case when we have an experience, nothing comes into being. When the experience stops, nothing ceased to be.

    I’m not sure have made any progress on these issues.

  7. 7. arnold says:

    Is progress possible via a blog, yes in thoughts–the role of thoughts toward a ‘higher level phenomenon’ could depend on what, in one’s body, the thought is of–a instinct, a sense, a emotion, a intent, a reflection…

  8. 8. John Davey says:


    I’m not sure have made any progress on these issues.

    Why would we ? This isn’t science. What it feels like to be a human being hasn’t changed for tens of thousands of years. The Buddha’s analysis of mental processes looks more scientific and accurate than that which the greeks did, committed as they were to a certain notion of human perfection. But they did their stuff centuries after the Buddha.

    Analysing what goes on in your brain is open to everybody. We are all consciousness experts. There is no bona fide expertes, no restricted body of knowledge that can develop in isolation. Progress in that sense is an impossibilty.


  9. 9. lorenzo sleakes says:

    Thoughts are consciously experienced. Hume thought thoughts were made of the same stuff as ordinary perception, that is the same qualia, but more lightweight, temporal and ephemeral. We seem to have some conscious control over our imagination in a way that we dont over external perceptions. In some way we can rotate images in our mind’s eye and experiment with possibilities.

  10. 10. arnold says:

    sleakes, “experiment with possibilities” to what end–qualia or physical transformations or…

    …Is any/all thought, even instinctive thought, the only means we have in-the-balance of our apparent evolution…

  11. 11. Shaikh Raisuddin says:

    If we know what memory is?, we can know what a thought is.

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