Importance of Doubting the Common Sense: Fish Doesn't Know It is in the Water
This is water: David Foster Wallace 2005 Kenyon College Commencement Speech
A commencement speech given by an award-winning American novelist, David Foster Wallace (February 21, 1962 - September 12, 2008) at Kenyon College at 2005 points out about importance of figuring out what really matters to you.
There are two fish swimming along and happened to meet an older fish swimming the other way who said, "morning boys, how's the water?" And two young fish swim on for a bit and eventually one of them looks over the other and goes "what the hell is water?"
In the speech, he pointed out what really matters is usually invisible and never be a topic to talk about. Thus, it's always important not to make an unwarranted assumption and conclude it for your own reason. Take a step back and see the bigger picture; you might be able to see the world around you differently. However, it's rather weird that he committed suicide three years after the speech.