Ancient philosophers seemed to do a lot more than their modern brethren. Zeno wandered around Greece with only a tin, making witty remarks. Pythagoras taught his students from behind a curtain and told his followers not to eat kidney beans. Socrates had public fights with his wife and beat the system by drinking hemlock before he could be executed.
Modern philosophers smoke cigarettes and stare at the camera with brooding angst. They have bad hair and dress in black. They write books. They drink to excess. They probably don't get along with people very well and can't speak without using big words and technical jargon. They're never seen eating and many of them begin to melt under direct sunlight.
When did things change, and who changed them? Of course modern philosophers are just as human as ancient philosophers, but there's no doubt philosophy took a weird turn at some point, and it's never recovered. Originally philosophers argued about the unifying element of the universe (theories ranging from earth or water to an elusive substance called mind-fire), the nature of the good life, and the best way to argue. Philosophers since the 17th century have developed an elaborate terminology to discuss esoteric concepts. What happened?
There was once a philosopher named Rene Descartes. He lived in France and read novels instead of learned works. He wore fashionable clothes, which was generally considered unfashionable among philosophers. The important thing, however, was his way of proving things. Before him, truth was universal. Appeals in defense of new theories were made to truth, because it had no human arbiters. All individuals were subject to the supremacy of truth. It was a very outward-looking approach.
Descartes changed all that when he looked inside himself for answers to his questions. His first concern was with his own existence, but instead of appealing to universal truth he used the fact of his own thoughts as his starting place. His famous cogito ergo sum (I think, therefore I am) was a foray into solipsism (one can only prove one's own existence), and the start of modern philosophy. Man was now the arbiter of truth because it began in the individual; if man must first prove himself before he can prove God or truth, there is no centralized point of reference for mankind in general.
The primary act of ancient philosophers was contemplation. Built on observation and association, contemplation is an outward-focusing act designed to understand the world and its operations. Modern philosophers are mostly introspective, looking inside themselves for answers to man's questions. Since they are men attempting to answer questions about mankind, they rely on experience and perception to cohere and relate knowledge. Observation is still key, but it is inwardly-focused rather than externally oriented.
Both approaches to philosophical endeavor are appropriate. Christian thinkers have long understood the need for both contemplation and introspection (which they tend to call meditation), realizing that as Christians they need to understand God, mankind, and self in order to be fully balanced.