There are two major schools of skepticism called as Academic and The Pyrrhonian . They are originated in ancient Greek philosophy.
Academic skepticism derives its name from the Plato’s Academy which was highly inspired by the remark attributed to Socrates,” All I know that I know nothing” . As said by Arcesilas (c.315-241 B.C.) and Carneades (c.213-129 B.C.) , This skepticism maintains that nothing can be known for certain.
The standard greek perception between knowledge which means episteme and opinion which means doxa. If a proposition cannot be shown with the complete certainty which can also mean it might be false and it does not qualify as a true knowledge which is consign to the status of opinion. As per the academic skepticism both our senses and our reasons which are unreliable to some extinct so that we can never claim ti know the absolute truth or any real knowledge. The pyrrhonian skepticism is named after Pyrrho of Elis (c.360 -275 B.C) which is a figure who is portrayed in secondary accounts as a complete skeptic eminently in the ethical manners. The mental misery and misfortune comes from seeking knowledge in the field of values therefore Pyrrho is said to have suspended judgement, thereby attaining the state of mind known to Greek Philosophers as “ATARAXIA”. Pyrrohonian skepticism which was known as distinct theory by Aenesidemus (c.100-40 B.C.). It was Aenesidemus who “assumed” and “doubters”. The two major school academic and pyrrhonian skeptics besieged “dogmatic philosophers who claimed to possess certain amount of knowledge with their take over with differed incomparably.The twp schools of skepticism it was the Pyrrhonian which was intended to influence of the Western philosophy because there were no major writings of the academics which survived which ruined of time. Around 200 A.D , the Greek physician Sextus Empiricius wrote an excellent and extensive account of Pyrrhonian skepticism.