I'm not going to talk about only one author of my specific field, the aesthetic, because there are so many different kinds of thinking trends, that choose only one writer will be very difficult and impoverish the importance of the influences of different school thoughts.
But, without doubt, one of the most important author that open the modern thinking was Immanuel Kant.
Immanuel Kant was a German philosopher born in 1724, in middle of the age of Enlightenment, when was the primacy of the reason, concept taken of the ancients Greeks philosopher and articulated under the Decart's postulate "cogito ergo sum" or "I think, therefore I am".
The writes and critics of Kant, based in thinking about the human works, influenced different areas like science, politics and obviously aesthetic.
His most important work for the aesthetic was the "Kritik der Urteilskraft" or "Critic to the faculty of Judgments".
The critic talks about the special condition of the aesthetic judgment, in the relation of representations and the same subject, opening in that way the after reflections and critics about subjectivity and arts.