How can there be collisions in Hashing functions?

The pedagogical aspect relates to the fact that the thread's OP clearly isn't lacking in intelligence nor knowledge, and I would've expected that some of the explanations would be sufficient. I found it interesting as a case study in learning/teaching.

The philosophical perspective relates to the link between our perspective of the world and the actual truth underlying it. The thread's OP was quite certain about the fact they were claiming as true, and was actually making a good argument for it. At least, the argument was good insofar as it was logical and wasn't falling victim to any egregious logical fallacy. It's interesting to consider consider this debate in contrast to a political debate which doesn't necessarily have such a solid underlying truth

On a personal note, I'm also slightly envious of the "OH!" moment that the thread's OP is going to have when everything falls into place in their mental model of hash functions. I remember when differential calculus first "clicked" with me, and when statistical hypothesis testing "clicked" with me. I'm still waiting for monads to "click" with me.