Nope you're totally right that at some point you have to understand how the Prolog engine actually tries to evaluate things. This is not just for performance, b

Nope you're totally right that at some point you have to understand how the Prolog engine actually tries to evaluate things. This is not just for performance, but as I allude to in the case of IO, sometimes necessary for correctness. Usually this is just knowing that Prolog does backtracking, but it can be more involved depending on your performance needs. But often for a complicated enough project you will find yourself resorting to cut quite a bit. What I meant by execution is more around how it feels to program in Prolog. So many things that feel like "hmmm I need to call this function and then this function here", etc. in other programming languages are just "oh, I just need to substitute a variable here" in Prolog. It's a very interesting world to remove the entire concept of "return" from your lexicon (e.g. a function returning a value).