A mindset of questioning or not easily accepting claims; often used in contexts like science, philosophy, or personal judgment.
You should listen to his explanation with skepticism.
A healthy skepticism is necessary for scientists.
Compound of 懐疑 (かいぎ, 'doubt, skepticism') and 心 (しん, 'mind, heart'). The exact historical derivation is uncertain, but the word follows a common pattern for abstract nouns expressing mental attitudes.