Aristotle was the last philosopher to describe the world cheerfully. Diogynenes and the Cynics who came after saw the world as something to recoil from, as something dangerous and doomed.
In the third century BC, Cynicism became the most popular doctrine. But it did not appeal to those who had political, scientific, or artistic ambitions, but to those who were severely disappointed with life, and required a philosophy that would justify their resentment at authority.
The best parts of Cynicism transferred into Stoicism, which was a more complete philosophy.
Skepticism, on the other hand, was a philosophy that appealed to the lazy, since it equated men of learning with ignorant men.
The man of science thinks that he has an idea about something but he is not sure if he is right, the intellectually curious man does not know how something works but hopes to find out, while the skeptic thinks that no one knows anything, or ever will know anything.
It is this conclusion that lends so much criticism to the skeptic school, for why we do not know anything for sure, we do know that some things are more probable than others.