The work of Galileo Galilei in the application of the telescope to astronomical observation met with rejection from influential sceptics. They denied the truth of his most startling reports, such as that there were mountains on the moon and satellites around Jupiter. In particular, some prominent philosophers, most notably Cesare Cremonini, refused to look through the telescope, arguing that the instrument itself might have introduced artefacts that produced the illusion of mountains or satellites invisible to the naked eye. To neglect such possibilities amounted to underdetermination in which argument for optical artefacts could be urged as being of equal merit to arguments for observation of new celestial effects. On a similar principle in modern times a prevalent view is that "extraordinary claims demand extraordinary proof."