The quest to understand human personalities has been going on for 3,000 years, or more. The Big Five Personality Traits are just the latest in a long line of models that take us towards that understanding.
And, it would be as absurd to think that the Big Five Personality Traits will be the last word on the matter as it would have been to stick with the four humours. But perhaps what the centuries of scientific development, and acres of statistical analysis, can assure us of is that we are honing that understanding.
How like the Big Five our 22nd Century model will be, we cannot know. But, for now, the best representation we have, of the fundamentals of human psychology, are the big Five Personality Traits. So, what are they?