"Denialism is motivated by conviction rather than evidence. It has been applied to a wide range of issues, including evolution and the link between HIV and AIDS. Deniers use strategies that invoke conspiracies, quote fake experts, denigrate genuine experts, deploy evidence selectively and create impossible expectations of what research can deliver. They rely on misrepresentation and flawed logic (P. Diethelm and M. McKee Eur. J. Public Health 19, 2–4; 2009).
By contrast, scepticism starts with an open mind, weighs evidence objectively and demands convincing evidence before accepting any claim. It contributes to the debate and forms the intellectual cornerstone of scientific enquiry."
in Kemp, Milne & Reay (2010) Sceptics and deniers of climate change not to be confused. Nature 464, 673.