I enjoyed the talk and agree with it in many ways, but perhaps a contrarian stance will stimulate some interesting discussion. Here's the steelman I can think of against that talk.

Hickey's fundamental contention is that whether something is easy is an extrinsic property whereas whether something is simple is an intrinsic property. Whether something is easy is dictated often by whether it is familiar, whereas simplicity lends us the more ultimately useful property of being understandable.

To which I'll counter with Von Neumann's famous quote about mathematics : "You don't understand things [simple]. You just get used to them [easy]."

There is no fundamental difference between ease and simplicity. Simplicity (of finite systems) is ultimately a function of familiarity. There's a formal version of this argument (which is effectively that most properties of Kolgomorov complexity when applied to finite strings are defined by your choice of complexity function, even in the presence of an asymptotically optimal universal language. In particular there is not a unique asymptotically optimal universal language, that is the Invariance Theorem is overhyped), but the informal version is that both simplicity and easiness arise from familiarity.

Indeed the fact that there is "ramp-up" speed for simplicity suggests that in fact what is going on is familiarity. E.g. splitting state into "value" and "time" is one way of thinking about it. But I could easily claim that in fact "time" complects "cause" and "state." Rather state machines where the essential primitives are "cause" and "effect" are the proper foundations from which "value" and "time" then flow (you can think of "effect" nondeterministically, a la infinite universes, and then "value" and "time" fall out as a way of identifying a single path among a set of infinite universes). Likewise Hickey claims that syntax mixes together "meaning" and "order" whereas I would could just as easily say that "order" complects syntax and semantics!

What of the idea of "being bogged down?" That "simple" systems allow you to continue composing and building whereas merely "easy" systems collapse and are impossible to make progress on past a certain threshold? I claim that these are not intrinsic properties of a system. They are rather extrinsic properties that demonstrate that the system no longer aligns well with the mental organization of a human programmer. However this is dependent on the human! A different human might have no problem scaling it.

Now hold on, perhaps, while simplicity is perhaps dependent on the human mind and humans all more or less have the same mental faculties. Perhaps we can't find a truly intrinsic property that we call simplicity, but perhaps there's one that's "intrinsic enough" and relies only on the mental faculties common to all humans. That is, returning to the idea of "being bogged down," there are systems whose complexity puts them beyond the reach of all, or at least most, humans. We can then use that as our differentiator between "simple" and "easy."

To which I would reply that this is probably true in broad strokes. There are probably systems which are are so arcane as to be un-understandable by any human even after a lifetime of study. But at a more specific level, the way humans think is very varied. The ways we learn, the ways we develop are hugely different from person to person. Hence I find this criteria of "bogging down" far too weak to support Hickey's more concrete theses, e.g. that queues are simpler than loops or folds.

When you're talking about things like love, hate, and fear, sure maybe those are universal enough among humans to be called "objective" or to have associated "intrinsic properties," but when you're talking about whether a programming language should have a built-in switch statement, I don't buy it.

For the purposes of programming languages, simple is not made easy. Simple is easy. Easy is simple. The search for the Platonic ideal of software, one that relies on a notion of intrinsic simplicity, is a false god. Code is an artifact made for consumption by humans and execution by machines and therefore any measure of its quality must be extrinsic to the humans that consume it.

Sometimes X is simple. Sometimes it's not. It all depends on the person.

As empirical evidence of this I leave this final exchange between Alan Kay and Rich Hickey where the two keep talking past each other, no matter how simple their own system is: https://news.ycombinator.com/item?id=11945722