So in the great scheme of programming languages, you had imperative languages like Fortran, eventually there was a paper “GOTO considered harmful” which ushered

So in the great scheme of programming languages, you had imperative languages like Fortran, eventually there was a paper “GOTO considered harmful” which ushered in a scaling-back of complexity to “structured programming” where you had named cells in which you could store values, and looping constructs like `while` and `for` to walk through them and manipulate them. Then we added on lexical closures over environments, which also take the form of “methods on objects” and “dynamic dispatch,” a bunch of different names for different forms of single-threaded OOP. Languages like GIL-ed Python and Ruby and Node.js continue this tradition today, while other languages add threading to have shared-state concurrent programming, with its vocabulary of locks and race conditions and cache invalidation and transactions and commits and consensus algorithms and now CRDTs... But, other visions of programming have coexisted with this main educational vortex, including logic programming like Prolog. Actually, if you have heard of any of these alternates, you have probably heard of functional programming, which can be ahistorically understood as saying “hey these locks and races and all that, it's actually very complicated, maybe we could have a simpler model of programming for 90% of our work and only break out the Java when we really need it.” And you’re like “what will you replace it with?” and they respond “Template substitutions! It's all the power of lexicographic scopes, all the power of looping (via recursion), but when you want to express the really complex stuff you need templates that have side effects when substituted, we can give those scary names.” So you give me a sunbeam and a raincloud and I give you back a rainbow. If that's the functional programming idea then logic programming takes the same idea but adds unification and search. The idea is “ok but why do I have to fill in all the parameters to a template before I use it? I should just say “if light shines on a droplet-cloud it makes a rainbow, a sunbeam is a light, a raincloud is a droplet-cloud, hey language, what are all the things that make a rainbow?” Functional programming was based on the function, the template, the “I take these args and produce a structure looking like such-and-so.” Logic programming is based on the Horn clause, “X verbs Y, for some entities X and Y that I maybe know about and some verb that I am being introduced to.” Basic things that logic programming does very well, OOP kind of struggles with. You can kind of understand this if you have written a SQL query. The verbs can be thought of as tables that foreign-key to X and to Y, if you want to write OOP to solve a logic puzzle you have to choose explicit ways to search or brute force... SQL DBs come with B-trees and indexes to solve a lot of these problems. Whereas with Prolog you just write the pattern to match and the new pattern to emit. It's a rather different take on what the building blocks should be.