1989: Iain M. Banks' The State of the Art depicts the Culture secretly visiting Earth and then deciding to leave it uncontacted, watching its development as a control group, to confirm whether their manipulations of other civilizations are ultimately for the best. 1989: Bill Watterson's Calvin and Hobbes comic strip for November 8, 1989, alludes to the possibility of an ethical threshold for first contact (or at least for the prudence of first contact) in Calvin's remark "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."