When we credit Montaigne as the originator of the essay, it’s not because he was the first to write in prose on factual topics — it’s because he turned declamation into conversation. … A Montaigne essay, like a Shakespeare soliloquy, gives us the impression that we are in 
the presence not of a disembodied, opinion-spouting voice, but of a real person.
Long after those essays lost their relevance, long after the second-hand reports from the Americas and meditations on 16th-century French politics ceased to be news, they have maintained their appeal because they are a personality embodied. And the foremost trait of that personality is freedom: freedom to take up and turn over absolutely any subject in human experience, on any prompting or none; to follow any tangent simply because it catches his eye; to begin and end a continent apart, or simply to trail off; to know for the simple sake of knowing.
In Montaigne’s day, that freedom was the privilege of an aristocrat. Today, unless we trade it away for a mess of relevance, it’s the birthright of anyone with a high school education and an Internet connection.