What makes people irrational thinkers?

[Belacqua]

So what's the genuine distinction between mind and soul, other than there are two different Greek words for the things?

The description I gave above was: 

Soul is more generally about the structure of our animate lives — it is our animation and how our animation functions. The Latin is anima. This includes but is not limited to the actions of the mind. It also includes the activities that the rest of your body is up to right now, including whatever your liver and your gall bladder are doing.

The simplest possible answer is "that which makes us alive." 

Greek philosophers defined the soul in various ways, some of which included some of the actions of the mind. 

As you might expect, Aristotle's answer was the most worked-out, consistent, and hard to argue with: "a system of abilities possessed and manifested by animate bodies of suitable structure." 

https://plato.stanford.edu/entries/ancient-soul/