Try this. When you step out of bed in the morning, open the curtains, take a big breath, and exclaim: What a wonderful day! I can’t believe how rational people are!
It’s because somebody, say Plato, opened the curtains one morning, looked out at the world and said Oh… My… Gawd! What is wrong with people?! Can’t they think straight!? that Western Analytic philosophy, was born. Of course I’m taking (humorous) liberties here. The point I make is that philosophy began by making observations about the world and thinking critically about them. Thinking itself, and how it corresponds with our observations in the world, also became an object of analysis. It seems that somewhere in our black boxes we come to know something about the world, whatever that might mean. And it seems that whatever is going on in our black boxes has some causal relationship to our actions. So notwithstanding you’ll hear almost as many definitions of philosophy as there are philosophers, (Western Analytic) philosophy is, in practice, a critical analysis of the core concepts by which we navigate the world. And there is good reason for this critical analysis because whatever goes on in our black boxes seems to play some role in our propensity to burn witches, waterboard prisoners of war, and build weapons of mass destruction. You know, that old saw about the sorts of things humans get up to when we’re left to play without supervision by an adult.
Plato conceived of philosophers as watch-dogs, or guardians of the herd, i.e. the everyday people in his ideal state. Plato envisioned philosopher-kings who would serve as both leaders and benevolent protectors of his Republic. I think it’s fair to say that this sentiment perdures in modern philosophy. In her capacity as an analyst, the philosopher offers her critical arguments to others, as in: Hey, I’ve thought a lot about this, and here are some reasons why you might not want to burn that woman (me?!) at the stake. Hence, we presuppose others are reasonable; i.e. that others can be reasoned with. Otherwise there’s no sense in our trying to appeal to another’s reason with an argument. But here’s the clincher. I doubt any one of us stands in the window, as I suggested, and wonders at how rational people are. Which means we also presuppose others aren’t reasonable; i.e. that people can’t be reasoned with. Well, some others, we grumble, and proceed to name them. We may even grudgingly admit that all humans are unreasonable about some things some times. Okay, well, yes, and sometimes even us. Just not near as often nor as extreme as the hoi polloi.
If we believed people were completely reasonable, or completely unreasonable, we’d not have much reason for philosophy. In the former case there’s be no need, in the latter, no hope. Our discipline rests on this tension, and it’s what makes doing philosophy so interesting. Humans are admixtures of internal and external processes, one of them being the want to make sense of ourselves and others. Since we share living together, this is a pretty powerful want, for philosophers as much as anyone else. The problem is, when we’re Plato in the window, raising our fists like intellectual curmudgeons, we tend not to see our own reflections in the glass.