Scepticism is the attitude itself — the habit of doubting a claim, or doubting that something will happen, until there is a good reason to believe it. You can feel scepticism about one small thing (“scepticism about the weather app”) or carry it as a way of thinking. In philosophy, scepticism is a whole school of thought: maybe we cannot really know anything for sure. Everyday English is milder: it just means “I don’t buy it yet.” Though actually, people sometimes say scepticism when they mean cynicism — assuming everyone is fake or selfish. Scepticism asks for evidence; cynicism assumes the worst. British sceptical / scepticism; American skeptical / skepticism. Neither spelling is “more correct”; they belong to different standard varieties.