Butterflies, mustard seeds, and misplaced critical thinking

I’ve just read Graham Moore’s The Last Days of Night, a novel based on the battle between Thomas Edison and George Westinghouse over AC vs DC electrification in the 1880s. This was a fascinating story*, but I’m taking off from it on a tangent today. The epigraph for Chapter 23 is a quote attributed to the architect and futurist Buckminster Fuller: “There is nothing in a caterpillar that tells you it’s going to be a butterfly”. Now, given my cringeworthy memories of what I was like in high school, I should be 100% behind this quote. The problem: as an entomologist, Buckminster Fuller was an excellent architect.

The quote, you see, is nonsense.

In fact, there are plenty of things about caterpillars that tell you they’re going to be butterflies. Granted, before the mid-1600s, western science hadn’t made the connection. Among those involved in figuring out that caterpillars turn into butterflies were the astonishing entomologist and artist Maria Sibylla Merian and the microscopist Jan Swammerdam. Swammerdam is particularly relevant because in 1669, he showed Cosimo II di Medici (the Grand Duke of Tuscany better remembered as patron to Galileo) something he’d discovered: imaginal discs. An imaginal disc is a little infolded pocket, concealed under the caterpillar’s exoskeleton and built of cells that will, in the pupal stage, expand and fold out to be come the wing (or the leg, or the antenna). An imaginal disc is something about a caterpillar that tells you it’s going to be butterfly, and we’ve known about them for 350 years.

So I thought critically about Buckminster Fuller’s attempt at wisdom; and as an entomologist, I was unimpressed.

Which brings me to mustard seeds. My father was a minister, and while I will admit to not always listening very carefully to his sermons, I remember one very clearly. Or at least, I remember the first few lines, which recounted the Parable of the Mustard Seed:

Another parable he put before them, saying, “The kingdom of heaven is like a grain of mustard seed which a man took and sowed in his field; it is the smallest of all seeds, but when it has grown it is the greatest of shrubs and becomes a tree, so that the birds of the air come and make nests in its branches.” (Matthew 13:31-32, Revised Standard Version, emphasis added)

 “Oh, come on”, I told my father, “what nonsense! The mustard seed isn’t the smallest of all seeds; in fact, it’s a pretty big seed. (OK, it’s no coco-de-mer.) The smallest of all seeds is almost certainly an orchid – some of the epiphytic orchids have seeds weighing less than a microgram (you’d need a hundred million of them to make an 8-ounce jar of Orchid Grey Poupon).

Now, the Mustard Seed Size IssueTM is old news, of course, endlessly rehashed by earnest evangelists and sophomoric teenagers like (at the time) me. It’s rather obvious, I hope, that the metaphor of the mustard seed communicates something** that’s independent of its literal truth or falsehood. Or at least, it wasn’t obvious to teenage me, when my father attempted to explain; but it’s obvious to me now.  And my memory of the Mustard Seed Size Issue gave me the jolt I needed to see the truthiness in Buckminster Fuller’s remark. Yes, as an entomologist I know it’s nonsense. But as a human, I should appreciate the underlying sentiment: indeed, sometimes the potential of something isn’t evident until it’s fully developed. Sometimes the (metaphorical) caterpillar really doesn’t tell you it’s going to be a butterfly.

This is, I think, just one manifestation of something we scientists do far too much: critical thinking, misplaced. We’re trained to think critically – but we should probably think critically about when that helps, and when it doesn’t. Often, we’re too eager to fall upon an incorrect detail and reject an important bigger picture. We’ve all seen Reviewer #2 do it. In hindsight, the grad-school journal clubs I was part of were little more than competitions to see who could most quickly find something – anything – wrong with a paper. And don’t get me started on social media. As a general rule: if you come to a situation determined to find its worst face, you’ll find it. There’s an inaccuracy; there’s a way to impute a bad motivation rather than a good one; there’s a way to see almost anything in society as a harbinger of the end times. But you know what? There’s always a way to do the opposite. There’s always a way to see the value of a metaphor that isn’t literally true. There’s always a way to see good (if failed) intentions. There’s always a way to see progress in small steps. Yes, sometimes you may look naïve when the worst case later proves to be true – but that’s a small price to pay to understand Buckminster Fuller’s point, and to see the best of the world as often as you can. Think critically about critical thinking.

© Stephen Heard  July 14, 2021

Images: Common copper butterfly feeding on wild mustard, © Zeynel Cebec  via Wikipedia.org CC BY-SA 3.0; imaginal discs of two fly genera, from Henry Pratt (1897), Imaginal Discs in Insects, Psyche 8:15-30; mustard seeds © Dennis Wilkinson via flickr.com CC BY-NC-SA 2.0

*^Easily the best novel about electrical transmission I’ve ever read. OK, I couldn’t resist that, but obviously it’s about the people involved: Edison and Westinghouse and Nikola Tesla; JP Morgan; the opera singer Agnes Huntington and the young lawyer Paul Cravath. Thoroughly recommended.

**^Whether or not you happen to subscribe to any version of Christianity, of course. I’m analyzing the parable of the mustard seed here as a metaphor, not as a religious statement.


18 thoughts on “Butterflies, mustard seeds, and misplaced critical thinking

  1. Katie

    This is what I needed to read and think about this morning. Thank you. I don’t know how I found your post, but I had it up on my browser for the past day or so and just now read it.

    Liked by 2 people

  2. Jeremy Fox

    I’m interested to see Ambika and Angela comment so positively on this post, given that both of them are–rightly!–known in part for important *critical* work. Work that says (in so many words) “This thing that everyone thought they knew? It’s wrong, for reasons X, Y, and Z. Or at least, less right than we thought. Or at least, it’s still an open question if it’s right or wrong.”

    I’m sure no one would deny that we ecologists sometimes err on the side of being too critical and not seeing the grain of truth (or truthiness) in some bit of ecological research. But clearly we also sometimes err on the side of not being critical enough–ecology certainly has its “zombie ideas”, ideas that should be dead but aren’t. I have no idea how to actually quantify which kind of error is more common among ecologists, or more consequential for the direction of the field. But let’s not let that stop us from talking about it. 🙂 So, Stephen, I take it from this post that you think it’s more common, and more consequential, for ecologists to be too critical, rather than not critical enough?

    Liked by 2 people

    1. ScientistSeesSquirrel Post author

      More, Jeremy, that we too often apply the critical thinking that’s appropriate in evaluating a scientific proposition, but apply it either misguidedly (rejecting a large idea for a flaw in detail) or misplacedly (which isn’t a word, but it is now) by applying it out of its proper sphere (as in my rejecting the caterpillar metaphor).

      Liked by 2 people

      1. Ambika Kamath

        For me it comes down to the spirit of the critique, “We’re trained to think critically – but we should probably think critically about when that helps, and when it doesn’t. Often, we’re too eager to fall upon an incorrect detail and reject an important bigger picture.”. Critique is essential (obviously I think so!) but to what end? What are we growing, after having cut something down? Too often what we’re growing is nothing, or more of the same.

        Liked by 1 person


    As a teenager, I also wondered about that mustard-seed parable. OK mustard seeds are pretty small and they might be the smallest seeds familiar to the original intended audience. But does mustard become a mighty tree? I didn’t have Wikipedia then, but I do now, and it says that Brassica nigra can grow to 8 ft. Personally, if I were retelling this story in Eastern North America, I think cottonwoods would be a good candidate for this metaphor.

    Liked by 2 people

    1. ScientistSeesSquirrel Post author

      8 feet is pretty impressive for a mustard, I must admit.

      Here’s what I wonder about cottonwood: does the average person realize that that fluff (1) comes from cottonwoods; and (2) has seeds in it? I’m going to guess ‘often but not always’ for (1), and ‘rarely’ for (2). But perhaps I’ve allowed you to pull me off topic. Squirrel!



    I think what I’m trying to get at, is: wondering about that mustard seed that grows into a tree and getting driven off topic is creative thinking, something we tend to try to encourage. Rejecting the main point because the metaphor is flawed is excess critical thinking. Or rather, it’s inability to recognize a metaphor when you hear one. Being critical of ideas is usually useful, being critical of detailed facts is sometimes essential, sometimes misguided, being critical of spelling is usually misguided.

    (And I’ve spoken to people who think the fluff is pollen that can give you allergies!).

    Also, I wonder about how we define ‘science’ when we say that western science didn’t know that caterpillars became butterflies until the 17th century. Surely most farmers had figured this out (in Europe as elsewhere). So when does knowledge about the natural world become ‘science’, when it attracts the attention of the sort of person who writes?

    Liked by 2 people

    1. ScientistSeesSquirrel Post author

      Good analysis on metaphor, I agree.

      Re: farmers “vs” scientists – wouldn’t be the first time that traditional ecological knowledge was out in front of publication. But whether farmers had figured this out is an interesting question! Folk belief in spontaneous generation far outlasted scientific belief, so it’s not obvious to me that metamorphosis has to be different.

      Liked by 1 person

    2. Christina Baer

      I’m late to the party here, but this reminds me of the following (Hunn 1982, American Naturalist, p. 381), about the naming specificity that a Mexican Mayan language applies to caterpillars and adult Lepidoptera: “These same Tzeltal Indians exhibit strong preferences for those parts of their zoological universe they consider worth bringing classificatory order to. For example, adult Lepidoptera (butterflies and moths) – the subject matter of a classificatory obsession of certain civilized folk-are of very little interest to the Tzeltal. Yet their larvae (caterpillars, cutworms, etc.) are carefully sorted into 16 terminal folk taxa in Tzeltal (Hunn 1977:280-285, 301-306). Some lepidopterous larvae are edible, others attack crops, and others acquire painful defensive ornamentation. The adults lack these characteristics. As a general rule, larval Lepidoptera are specialized for feeding, adults for mating, hence their contrasting cultural impact on the Tzeltal. There is, of course, ample morphological diversity visible to the human eye among both adult and larval Lepidoptera upon which to base a classificatory ordering. Yet for swidden farmers the larvae are noteworthy, the adults are not. The classificatory detail applied is clearly in large part a function of practically motivated interests in the Tzeltal case, but of a compulsion for intellectual order on the part of the civilized butterfly fancier. ” This article does not say anything about whether the Tzeltal traditionally recognized caterpillars and adult leps as different stages of the same organisms, but maybe the 1977 book would have something. I would think that this would be pretty evident for species that pupate on their host plants (including many butterflies), but there are a lot of moths that pupate in the leaf litter or underground.


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  6. The Devil Unbound

    This is a very elegant call to a meta-cognitive commitment to knowledge. Thinking about thinking. I agree with the sentiment: sometimes the poetic value of something carries great lessons that are worth observing. But at what cost? Is a piece of conventional wisdom worth opaquing or ignoring an objective truth?

    I think this also points to the problem of the seemingly absolute relationship (in language) between style and substance. A true thing expressed badly is a lie,a and vice versa. Fuller’s aphorism had substance only in the context of his intended message, but it was a lie in any other.

    Tell me, and I ask this because I’ve pondered this for a while: does a lie have value or utility if it points someone in the right direction? Does disinformation have positive ethical value if it leads society towards a better state?

    I genuinely look forward to your answer.


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