What topic do you have the most knowledge, and can you explain it so a child can understand it?

Wastewater - Separating liquids, solids, and gases for responsible re-use.

Botany - Learning about the natural world and how it relates to everything you know and love (i.e. without plants there would be no humans, chocolate is yummy, grasses feed the world, etc).

Flushable wipes are not in fact flushable.

As a field of study, it's the study of two-player games of perfect information (so think chess, not football or poker) in which each player may make countably many moves (you can also look at uncountable-length games but it's not common). I'll give you more detail than I would a child :P

Each player takes turns to move. You can encode the moves they make as coming from some set - for example they might just play numbers. The rules of the game are imposed by a winning set, which is a set of countable-length sequences of moves, and we say that player I wins if the infinite sequence of her first move followed by player II's first move followed by her second move, etc, is in the winning set. Otherwise player II wins. (There are no draws, which technically means chess falls outside the scope of this setup, but it turns out not to be a big deal)

(This allows you to encode what moves are allowed by the rules - you just say that any sequence which contains a move where that player broke a rule is a loss for that player, regardless of what comes afterwards.)

Each winning set defines a different game. The property of determinacy is a property of sets of infinite sequences which says that there is a winning strategy for either player. A strategy is just a function which takes the finite sequence of moves up to that point in the game and tells the player (the player for whom the strategy is) what to do. A winning strategy is one which, if followed, always results in a win for that player.

If we modify the rules of noughts and crosses (tic-tac-toe) so that draws are arbitrarily decided to give a win to player I, we know that this (finite) game has a winning strategy. In fact, any finite game has a winning strategy (or, if there are draws, this means there is a non-losing strategy). The outline of the proof is that if player I does not have a strategy to get to one of the (finitely many) winning states, then we can find a strategy for player II which avoids those winning states. (Remember, winning states are winning for I).

So, which games are determined? Are all games determined? Well, it's actually easy (through a diagonalisation argument, same as proving uncountability of the reals) that not all infinite (countable-length, that is) games played with natural numbers (as moves) are determined. But you can create a way of categorising the sets of countable sequences of natural numbers (i.e. the possible winning sets) by a kind of complexity. This is the basis of descriptive set theory. It starts with topology: you can define basic open sets in this space as those sets consist of all infinite sequences which share a common finite prefix. Closed sets are the complements of open sets, as usual. But then you can define a hierarchy of complexity where the next level are countable unions of closed sets, then the next level are countable unions of complements of countable unions of complements of open sets. (An introduction to descriptive set theory will say more about this).

It's quite easy to prove that all open sets and all closed sets in this hierarchy of complexity are determined. It's a little harder to prove that the second level is determined, and harder still to prove that the third level is. Eventually a guy named Tony Martin (D. A. Martin) proved that all Borel sets in this hierarchy are determined. If you know your analysis, the Borel sets are exactly what you're thinking: they're the sets formed by all arbitrary countable unions, intersections and complements of open sets.

The interesting thing about this proof was that it needed a huge amount of set theoretic "power". Most ordinary mathematics like analysis doesn't need all the axioms of set theory, but this needed a massive chunk of them. This makes it interesting to set theorists because it tells us something about the relationship between something quite concrete: complexity of sets and strategies for easily-defined games on the one hand, and something quite abstract: the axioms of set theory. This pattern continues higher up: more determinacy can be proved if you assume even stronger axioms, going beyond what is typically included in set theory.

Sounds great, because I am!

There's a barrier between what we hear and how we feel about it (which will then be expressed in words and action) and that's the barrier of ideology plus self-beliefs (what we think). Plus, how mentally agile you are will decide on how quickly you reply (that's why folks with ADHD can say and do some wild, impulsive shit, for instance). By analysing our beliefs critically and fearlessly, and tearing down the ideological house of cards that causes us cognitive dissonance and impedes us from reaching the right conclusions in many areas of our lives, we can better deal with the world and how it 'makes us' feel. Going from "people are not to be trusted" or "all women are sluts (but somehow they will never date me)" to "people are fundamentally good, but flawed to different degrees and in different ways and there's no need to live in fear" and "women and men are sexual creatures, most women are not prostitutes and this is just the way I've coped with my lack of success in the dating world and with the feelings of worthlessness and despair that come with it", for example, will 100% help you better handle your emotions.

There's nothing to do about mental agility though, I've found, besides being permanently medicated/sedated or high on weed. And none of those sound healthy/ideal. 🤷😅

Oh, it's just what I've noticed in myself, and others when I ask them what they believe in and the convo goes from there.

It seems that in the end it's one of two things... There's what's known as the Epicurean paradox or the problem of evil, where the confusion arises from many sources: forgetting about the existence of free will and the causal chain of events, semantic nonsense or even simple immaturity. This is the one that's just all fluff, all wind, but words can kick one's ass, especially if you live more in words than in reality.

And then there's the one that I respect a little bit more: while the beginning of the causal chain that we can conceive (so, embedded in/attached to space and time) is evidently not a source of it, but also since things exist today we can't deny the 'proto-thing' existed then I can somewhat accept you telling me that this essence we call matter and energy was always there and God is not necessary and etc etc. God has been understood for millennia as the 'prime engine' and unmoved mover, behind the universe and before it, the One that 'comes from nothing' that we have to accept because nothing comes from nothing and things exist. But many folk just skip that part and say "things exist, that's all I can see and that's all I will believe in". That's fair, but I better not see you making any logical inferences then, lol.