Philosophy began when individuals began to take a look at the world around them and see "patterns" or "laws" at work. To say that they were "looking" for a rational explanation is probably not the best way to put it since the first philosophers had no idea what reason or logic was. Rather, it was by the observance of things around them that led to the idea that something like rationality existed.
The first western philosopher was a Greek living in Miletus on the western coast of Asia Minor. His name was
Thales. He supposedly predicted an eclipse in 585 BC, but the importance of his work goes further than Astronomy. He began to draw particulars from generals. After physical phenomena, things such as history (laws of the way history works), medicine (laws governing the physical body), and finally ethics (laws about how one should live) were studied.