The lambda calculus is an entirely arbitrary way to organize things in math. It’s not based on nature or truth at all.
The real problem, though, is that FP doesn’t do anything well. It’s never the fastest method of programming, which means that it needs to excel in some other way for its proponents to be right about it. Is it the most maintainable? Maybe if you have zero side effects but then any paradigm would be in that case. Once you introduce state, it becomes a nightmare to maintain, unlike OOP. It’s certainly not the most readable.
> The lambda calculus is an entirely arbitrary way to organize things in math. It’s not based on nature or truth at all.
Lambda calculus, category theory, and logic are essentially 3 sides of the same coin (the Curry-Howard-Lambek correspondence). The rules of lambda calculus match those of natural deduction. It runs quite a bit deeper than you're suggesting here. It's not just some arbitrary formalism.
Glad to see these comments because the parent's "it's math therefore from a deity, and much more correct than your grubby computer stuff" is so often trotted out. It turns out that there's no directionality to the relationship between mathematics and computers -- they're the same thing and one can be transformed into the other. e.g. Lambda Calculus is just a kind of VM someone came up with that can be used to model certain structures. Same for Category Theory, and same for Logic. So you might as well say that Lambda Calculus is derived from IBM 360 assembler language than the other way around.
The real problem, though, is that FP doesn’t do anything well. It’s never the fastest method of programming, which means that it needs to excel in some other way for its proponents to be right about it. Is it the most maintainable? Maybe if you have zero side effects but then any paradigm would be in that case. Once you introduce state, it becomes a nightmare to maintain, unlike OOP. It’s certainly not the most readable.