This video contains many serious misrepresentations. For example, it makes a claim that Alan Kay only started talking about message-passing only in 2003 and that it was a kind of backpedaling due the failures of the inheritance-based OOP model. That is a laughable claim. Kay had given detailed talks discussing issues of OOP, dynamic composition and message-passing in mid-80s. Some of those talks are on YouTube:
The dates are the dates of the sources, he says in the talk he wasn't going to try to infer the dates these ideas were invented. Also he barely talked about Alan Kay.
From the video: "It's like, yeah, he said that in 2003, right? He said that after a very long time. So why did he say it? It's because 10 years earlier, he was already saying he kind of soured on it."
Casey says he “didn’t really cover Alan Kay” https://youtu.be/wo84LFzx5nI?t=8651 To me that says that Kay wasn’t a major focus of his research. That seems to be reflected in the talk itself: I counted 6 Bjorne sources, 4 Alan Kay sources, 2 more related to Smalltalk, and about 10 focused on Sketchpad, Douglas Ross, and others. By source count, the talk is roughly 18% about Alan Kay and 27% about Smalltalk overall - not a huge part.
As far as the narrative, probably the clearest expression of Casey's thesis is at https://youtu.be/wo84LFzx5nI?t=6187 "Alan Kay had a degree in molecular biology. ... [he was] thinking of little tiny cells that communicate back and forth but which do not reach across into each other's domain to do different things. And so [he was certain that] that was the future of how we will
engineer things. They're going to be like microorganisms where they're little things that we instance, and they'll just talk to each other. So everything will be built that way from the ground up." AFAICT the gist of this is true, Kay was indeed inspired by biological cells and that is why he emphasized message-passing so heavily. His undergraduate degree was in math + bio, not just bio, but close enough.
As far as specific discussion, Casey says, regarding a quote on inheritance: https://youtu.be/wo84LFzx5nI?t=843 "that's a little bit weird. I don't know. Maybe Alan Kay... will come to tell us what he actually was trying to say there exactly." So yeah, Casey has already admitted he has no understanding of Alan Kay's writings. I don't know what else you want.
I nearly jumped out of my proverbial seat with joy when Casey talked about it being about where you draw your encapsulation boundaries. YES! THIS IS THE THING PEOPLE ARGUING ABOUT OOP NEVER SEEM TO ADDRESS DIRECTLY!
Honestly would love to see a Kay and Casey discussion about this very thing.
I find the discussions about real domain vs OOP objects to be a bit tangential, though still worth having. When constructing a program from objects, there’s a ton of objects that you create that have no real-world or domain analogs. After all, you’re writing a program by building little machines that do things. Your domain model likely doesn’t contain an EventBus or JsonDeserializer; that purely exists in the abstract ‘world’ of your software.
Here’s a thought: Conceptually, what would stop me from writing an ECS in Smalltalk? I can’t think of anything off the top of my head (whether I’d want to or not is a different question). Casey even hints at this.
This is probably the best Casey talk I’ve ever seen and one of the clearest definitions of ‘here is my problem with OOP’. I don’t agree with everything necessarily, but it’s the first time I’ve watched one of these and thought “yep they actually said the concrete thing that they disagree with”.
https://www.youtube.com/watch?v=QjJaFG63Hlo
Also, earlier versions of Smalltalk did not have inheritance. Kay talks about this is his 1993 article on the history of the language:
https://worrydream.com/EarlyHistoryOfSmalltalk/
Dismissing all of this as insignificant quips is ludicrous.