Philosophical term referring to the doctrine that true knowledge is unattainable, or a general attitude of doubt.
From a standpoint of skepticism, he doubted every claim.
An adjective meaning 'skeptical'; 懐疑主義 is the noun for the philosophical doctrine or attitude.
Compound of 懐疑 (かいぎ, 'doubt') + 主義 (しゅぎ, '-ism'). The exact historical derivation is uncertain; the spelling is conventionally associated with the meaning.